| It is with great relief that I’ve found the root cause of the passenger side stock turbo failure (long). Here’s the background of my turbo failure Video of my failed Turbo, Blown Turbo 1st Engine Pull, Failed Turbo Analysis. Cause: my turbo had a heart attack due to a blocked turbo oil inlet tube. The turbo bearing eventually suffered oil starvation under high boost conditions on a really hot day. The turbo oil inlet tube was blocked with nothing other than… oil itself. At first glance the below turbo oil inlet tube looks to be in good shape. Compared to the brand new one the original is relatively clean with the heat shielding and clips mostly intact. A perfunctory check of blowing air through the tube was impossible so I hooked up the air compressor to see what I could blow out with pressurized air. 
Here’s the baseline test video of the blow down characteristics of the air compressor tank set and vented to atmosphere.
Here’s the simple test pressurizing the tube from the back with 70 psi. Here’s the slightly more complicated final test which required me to remove the 3-way coupler off the block again with 70 psi. Yep! There’s definitely something not right here. Sounds like this guy is living in the tube.
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I start taking the tube apart. A closer look under the heat shielding reveals a much darker side. There is plenty of rust located underneath the entire length of the heat shielding. 
It’s interesting to note the similarity of the rust pattern located underneath this oil tube compared to the rust I’ve noted in previous posts underneath the exhaust manifold heat shield.
Links regarding manifold rust
Clearly condensation is playing a key role here though I don’t yet fully understand the mechanism. Next steps were to chop the tube up in pieces methodically in such a fashion as to minimize the disturbance of the original blockage. Obvious starting points for elimination were locations of the tightest bends. Here the bango and compression fittings were cut off and 3-way coupler removed. 
To my great surprise the pieces cut off were relatively clean, or at least they weren’t restricting the flow in any way. I confirmed with the air compressor the blockage was still within the pipe and continued cutting lengths at locations such that I could see through the resulting straight section.
Here were the first indications I was getting close.
The final cut was to cut the above piece in half. Below are the staggering results as close as my point and shoot camera would allow me. Complete blockage! 
The turbo inlet oil tube is approximately ¼” -- a very small diameter. The upstream orifice is 0.035” and was not restrictive at all to the 70 psi compressor air charge. This blockage is downstream of both the oil filter and the flow metering orifice.
So it seems the turbo oil inlet tube suffered from heat soak-back which caused coking when the engine was shut down. I found no indications of coking within the turbocharger itself or at the compression fitting leading to the turbo. This leads me to believe that coking occurred only when the engine was shut down and to my knowledge there were not many “hot shut downs” which of course are known to take a toll on the turbos. My turbo did die on a particularly hot summer day. The shutdown previous to the failure likely provided the coking and final blockage that ultimately was the straw that broke the camel’s back such that oil starvation of the PS turbo bearing occurred under high turbo rpm at the highway on ramp. I do not believe oil contamination caused this blockage as the previous owner was emphatic he did all necessary oil changes on schedule and used only Mobile 1 synthetic. For the most part I confirmed this with his City Garage receipts as well (he said he brought the Mobile 1 synth. to them for the oil changes). Careful examination of the location of the cuts shows the blockage occurred directly above the turbocharger exhaust housing – not at the pre-cat/downpipe.  
The location of the blockage is not visible while the engine is in the car. Clearly where the blockage occurred is a location inside the engine bay that gets really, really hot. Below are pictures of the PS turbo oil inlet tube while the engine was still in the car. The bango sits right next to the block and turbo exhaust manifold but that’s not the part that gets heat soaked. Incidentally I’d noticed the closeness of the oil line to the turbo exhaust housing on this side and took this picture to remind myself to rectify this while the engine was out. At the time I had no idea of the severity of this situation.
With the pre-cats (downpipes) off you get a glimpse on the RHS where the blockage occurred just above the turbine but not so far forward where the tube drops back down into the CHRA. I wonder if the level of the turbo oil inlet pipe at the blockage location is such that it doesn’t allow scavenging when the engine is turned off. Do you think I should bend the replacement oil inlet pipe such that there’s more slope when the engine is turned off and enhance the scavenging? I’ll look into this more when I put the pieces back together. Do you think I should buy a new turbo oil inlet line for peace of mind that another used one isn’t already half baked?
Below is the view underneath the battery. This is not where the blockage occurred. That would be forward (or upward) in this picture. 
I feel vindicated that in the end I found this out before rebuilding everything with new turbos. I don’t think there was anything I did to expedite this turbo failure and am confident that the rebuild will be successful and reliable too now that I understand what happened. To be sure I’ll test the oil system as mentioned in Damon’s Post before taking the engine to WOT. If any techies out there are interested in analyzing the coked oil line further I’ll gladly send you off a slice of congested tube free of charge. Just e-mail me your address.
Things I’ve learned that I’d like to share: 1. Heat shielding is much more important than you realize. Heat shielding certainly impacts reliability and can even impact performance. You best not remove stock heat shielding unless you understand and/or mitigate the consequences. In my case the ineffective shielding provided additional heat conduction through the added rust, and lack of turbo heat shielding ostensibly removed by JNE’s shoddy turbo techs strongly contributed to the coking where associated oil starvation caused the eventual downfall of this turbo. 2. I’ve heard it is common for the PS stock turbo to die first so if you are reading this beware of the sensitivity of the PS heat shielding and oil plumbing in your current setup, especially if you live down south. In my case the DS turbo oil inlet pipe had absolutely no restriction other than the production flow metering orifice. 3. I was considering installing inline oil filters but now that I understand the oil system better and its weak points I believe an inline oil filter will not provide additional protection for the turbo and could in fact compromise the turbo oil inlet system more than the stock configuration by adding additional oil volume in a location of the engine bay which is heavily heat soaked and susceptible to coking. 4. Because the turbo oil system is metered with a 0.035” orifice ANY blockage that makes it past the oil filter can have a devastating effect. In this 2009 example a pregnant crane fly found its way into the oil filter tree while TT XTZ was doing engine surgery. The result is absolutely catastrophic! (thanks again ConVerTT) Keep the engine covered and the oil filter on as much as practical when performing engine surgery. 5. If your wife or girlfriend can’t understand why you spend so much time doing Z car work yourself remind her of my story: the disservice previous mechanics paid me by omitting the heat shields costs me huge $$ in a turbo replacement. In the case of Z cars you’re better off having the work done by seasoned amateurs rather than shoddy professionals! 6. It’s incredibly important to have an air compressor if you own a Z car. The air compressor is critical for troubleshooting boost leaks and for recognizing oil system blockages in this case. Noobs reading this you’ll need to buy one eventually so might as well buy one today. 7. If you don’t stop smoking and eating fatty foods laden with salt your arteries will end up looking like my coked turbo inlet tube and inevitably you’ll suffer expensive, painful, if not fatal health problems just like the Z car. 
Had I not had the persistence to keep up this witch hunt over the past year I’m 100% sure I would have destroyed the new turbo within 500 miles. Thanks ConVerTT , zromtech, AliaZ, Bernie, BigTDogg, Evan_Wright (Ca), induetime, Turbodog (CT), ztunerz, Greg, LitlElvis, and all of you responding to my posts for keeping me focused on determining exactly how the old turbo failed. This has been a long time coming. Thanks for checking out my post.
OverZealous (CT) My General posts (click)
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Final Turbo Failure Analysis (long with pics) - 
