I have to agree if you are doing a complete exhaust. the 3 inch pipes fit like a glove. The race headers were tight compared to the hookers but I didn't have to cut a hole in the fender wells. For the street TTI's . For the track shop built or Hooker race headers if you can find them. We are building stainless for the new Duster using stainless copying the 2 inch hookers but they will be 2 1/8 inch. My theory is you can't take in what you can't let out. The rule of the scavenger effect goes out the door with power adders. Boost or nitrous. These by far were the best headers I ever used or installed. Just my opinion