ive never been pulled over for my exhaust yet
and ive had
hks hi power
ebay motoria thingie, (that sounded awesome)
invidia
straight 3"

but sean got pulled over in his red coupe for his fujitsubo that was as quiet as a mouse fart. theres no real science behind it, some cops are assholes, some arent.

i wish my car was louder sometimes, but not enough to really do anything about it.
only thing id probably do is a long tip n1 muffler, and have ranlet make piping.