nova ss, we/i run them on the brothers nova with a procharged 555 we had to double them up for the street. when we got to the track we took 1 set off and ran. reinstall the second set and the car never slowed down. you should check out DR GAS WEB SITE they have oval pipe to clear the bottom of the car were useing the pipe that would be the same size as 4" the stuff is very nice. good luck