not much. the main thing that restricts our tiny turbos is the catalytic converter located directly after the turbo itself. once that is gone, the exhaust moves air out of the way better and lets the turbo do what it can.In all honesty, how much top end is gained by adding full 3" exhaust to a 3" downpipe? That's with a stage 2 tune. I doubt it does much because the turbo has no top end.