I just got back from removing my 3" turbo back exhaust with TP and my big Greddy SPRL fmic from the car. I put back the stock stuff and I can tell you that it makes a huge difference. The car feels like it lost 50 or 60 whp It's still got the HKS cams and gears the walbro pump and 680cc injectors, but the exhaust and fmic seem to be a very important part of the cars performace. Another thing to remember is that those styrofoam peanuts are a ***** to get out of the FMIC and the pipes. Apparently a few remained behind and caused the throttle body to stick open a time or two, gave me a big scare and at midnight, troubleshooting and odd thing like thart is the last thing we wanted to do Anyway, we pulled out the intake pipe hose to the Throttle body and sure enough, we got the damned things out... No more problems Bottom line is that the open exhaust and free flowing FMIC are very good power mods......