well i was going in with my 04 neon SXT to get a custom 2.25in cat back pipe to fit iinto my r/t style muffler and wat did i find? neons already have 2.25in exhaust pipes. the pipe is 2.25 in from the cat back till about 4in b4 the end of the pipe where it turns into 2in. and then theres no need 2 change the piping into a bigger pipe. soooo for anyone else who wants 2 go get bigger pipes like me dont bother cuz ull look like an idiot just like me

 

there's nothing wrong with doing a 2.5" exhaust the whole way back, which would require that you upgrade all of the tubing that's already there. Of course, you'll need a larger opening on your exhaust if it's only 2"

 

The back piece of the srt-4 exhaust bolts directly up to where the muffler does on a 2003 to 2005 neon sxt. It sounds awesome and gives it a mean look.