Ok I can understand that if we change the breathing characteristics of the car its going to need a retune. My car right now has a 3" dp to a mp to a flowmaster muffler. Which I'm not sure if it is a straight through design or a chambered muffler. I'm trying to have my car ready for when Steve Kan comes to visit Florida. But I don't know if I will be able to have the muffler I want by then. If I get it tuned with the muffler I have on now. And then later on change to the muffler I will get (RE-Amemiya Dolphin Tail). How much will this affect the tune he does? I will not be changing the mp or dp. Just the muffler section.