| Biggest issue, especially given the age of these vehicles, is that the EGR system is highly prone to failure. When the EGR valve fails in it's most common of modes, the valve leaks and allows very hot exhaust gases to blow through it while in a boosted state. Normal operation prevents this as the valve's diaphragm receives boost pressure to increase it's sealing force appropriately. But when they fail at the valve body you now have a scenario that inevitably will lead to severe damage to your engine. Recirculating exhaust gases displace intake volume which reduces the metered airflow that the ECU uses to determine fuel delivery and timing advance. So right when the engine gets into making gobs of power, the ECU starts reducing fuel flow and advancing timing. Both of which are exactly the opposite of what you want happening while in boost. Additionally, the exhaust gases that are leaking back into the intake are incredibly hot which further increases the probability of detonation... adding a lean condition with too much timing advance to that and voila, you're onto your next engine build. I know that visual inspections in emissions testing can make this a problem for an owner in some cases and I wish I had something to offer to that regard. While this was considered in the development of the product it unfortunately just presented far too many complexities in the design to cater to it. I have more information to share to this regard though for those who live in areas with strict emission testing protocols..
Enthusiasts soon understand each other. --W. Irving.
Are you an enthusiast? If you are out to describe the truth, leave elegance to the
tailor.
Albert Einstein
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