I've searched the forum and found that stock exhaust is pretty much maxed. Im not willing to spend 1k for little to no gains. Is there a way to make the stock exhaust sound better such as straight pipes or etc? I have a 07 g35

 

Used setup won't cost you a grand
MD art pipes are a good thing to pair with regardless

 

Like Jersey said, the only way you will get any real gains is to swap out the oem cats with test pipes or HFCs.
OEM cats are where the biggest restrictions are.
But if you go that route either option tend to make the oem exhaust kinda raspy.

 

Will I still be able to pass emissions if I swap out the cats?

 

I think it depends on what state your in.
I know in California you will not pass emissions.
When I go in for smog I put the oem cats on to pass then put my HFCs back on afterwards.

 

Start with a good Y pipe, build from there