What you need to realize is that your dealing with a 3.0 liter engine with very small head ports, and very small valve lift.
With boost you increase air flow that effectively has a similar effect as increasing the engine size without increasing the head ports or valve lift.
When upgrading any engine you need to understand the flow restrictions of the set up, and make sure your increasing the flow in everything required to reach the desired result.The factory piping on the Z limits the power the most because the pipes are the most restrictive areas.
With stock turbos, the gain with pipes is huge, the gain with larger turbos and pipes is even greater, but not a lot greater with stock heads and cams because the head ports and cam lift of the stock Z engine are limiting the possible flow for larger than stock turbos at the same boost level.
The larger turbos will make dramatically more power at higher boost, but that requires higher octane.
The larger turbos will make more power at the same boost level with stock heads and cams because your still removing resistance to flow on both sides of the engine with the larger compressor and turbine wheels.
Again the reason the larger turbos do not make a LOT more power at the same boost level is because only so much air can move through the stock head port at the stock valve lift without increasing the boost. Newer engines have significantly bigger head ports, the factory cams have significant more lift, many have larger lift cams than would fit in the Z head.
Engines make power by the volume of air they move, so the GM engines with huge head ports and cams with the large engines are going to make power. If you want to outrun the GM cars that have big head ports and high lift cams that move a lot of air, you need to increase your head ports and cam lift, or force more air through at higher pressure with higher octane.
E85 for the cost and cooling effect is the best choice for increasing octane. On E85 your set up will make about 600 wheel HP. The AMS manifold could be why you are not getting the full desired result from your set up.
The AMS manifold is sold with only the raw cast openings, those openings for the head ports are all over the place due to core shift when making the manifold, so the head and manifold ports do not line up correctly. They also made the casting runners larger than others and that reduces velocity to drive the turbine. The MSP manifold is a very well engineered part, Mike Smith spent a lot of time maximizing the runner sizes to achieve the most equal flow to the turbine for a log manifold that has different length runners. Mike also machines all the openings, they are gasket matched to fit the head ports correctly.
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16:08:17 06/22/15
