I had APR stealth turbo back. It wasn't obnoxious, but it was not quiet either. But with stage II programming, it definitely adds a noticeable amount of power in the mid and top end, right where you want it on the track. I may be at The Glen II. May dad broke his motor and needs a new one. I think I have him convinced to just get a new Corvette, and if he does I'll twist his arm into going to WGI 2.