i dont know, nowadays, you can have an exhaust and still be a sleeper because of all the ricers. things that tip people off, opening your hood, not opening your hood if asked, bad idle, lots of gauges, or ripping by them at 25psi in 3rd gear. :-) i say go all out 3in, but i am all about how fast can the car be, not how fast can i make it but keep it a secret too. yea its fun to sneak up on people and smoke em, but you also dont want to get turned down for a race just because they "know" that they will win.