Hey guys, i drive a R32 GTR and i got epa about a month ago..
As my exahust i have a 3 1/2 inch cat back system and the car was way too loud for standard 90 DB, so what i did, i wealded a plate in between the front pipe and the cat....
This has brough me down to 88 DB making me just pass....
But make sure guys when you do this that the plate is propperly wealded to the cat with three 10 mm holse in the plate that you are going to weald also try not to drive the car not over 3 thousand rev's others wise you will blow your exhaust seals...
Guys if you get this and you have to go there, dont go there with just a plate in between, otherwise you will get a $500 FINE!!! at Maclouds
hope to be a help