A perty big gain removeing the egr valve no more hot exhuast back into the engine ,and now Iam at 10+psi of boost before I would see at wot 8psi brefly.
I adjusted the boost by this method
http://www.serenitysys.com/MB/Service_Info/Turbo_Tweak/tweaking_the_mercedes_617_turbo_.htm
PIA ,but worth it