I unbolted my exhaust at my down pipe to see what it would do at the track the difference was amazing!!! before i pulled 14.2@98.7mph the very next week on a warmer night with open exhaust I ran 13.44@103mph! I have Greddy power extreme 2 1/2 now but after this I ordered 3 Apex N1. I still cant believe my car is that fast!