I purchased an E92 with an AA Stage 2 SC on it. Haven't had any problems since day 1. Makes great power and compared to stock cars - doesn't really change the 'personality' - just enhances what's already there.
Best part about it: it drives like it's STOCK when you're just cruising around town, but when you get on it, watch out... lots of fun.
Only challenge is traction. 1st gear WOT is all but useless, 2nd and most of 3rd aren't much better.