Yep, iA does fine with autocross. I'm running in STF, but that's because mine is tuned. I'm not really gaining much from the extra power, but the higher redline is nice to maintain 2nd gear longer.
In my opinion, the iAs biggest stock weakness is the 5.5" wide wheels. I think that is what will keep it from being very competitive in the Street category. It's hard to get a good performance tire that's not too wide for the wheel and have wollowy sidewalls. And if you change the wheel width, then that's a bump to STF.