I never had my car on the dyno with my tti's. I can tell you what my car gained at the track consistently. I have a 4in crank motor with w5 heads. I originally had 1 7/8s tti's on it and went mid 9.70s at 137+ consistently. Put my 1 7/8s hedman hustlers on it and run mid 9.60s at 138.50+ consistently now. My hedmans fit great.... hedman makes a 2in header also. Hedman hands down if you want to go fast imop. Btw this was with no other changes.