i just got an 08 auto sedan and it isnt as loud as my friends older coupe, does it need to be broken in longer? its very quiet.
what will make it louder but keep the traditional g35 sound?

The stock sedans have always been known to growl quieter than the coupe. Although there's almost no way to match the exhaust tone to that of the coupe, you can make it sound better on your '08 sedan by adding dual intake (Fujita) and exhaust (there are some options for that, do some research).

i'd say get an intake, it'll sound awesome under WOT

get a fast intentions exhaust

Put a rabbid pit bull in the passenger seat

Drop in a V8

damn

test pipes or cat back exhaust or intakes

Start off with an intake. My coupe sounded a good bit better WOT when I added my intake. After that, I'd look into a Fast Intentions exhaust with some of their resonated test pipes (if they are available for the 2nd gen sedan)

Sedans have always been quieter than the coupes. If you want a louder growl, then obviously get an exhaust and/or HFC or test pipes.

.

exhaust.

Port the heads

i'd rather stay away from an aftermarket exhaust because the cops around here harasse people with those....i was thinking of a test pipe but dont want annoying cel problems so i guess the only way i can go is intake, right?

if i keep it close to the original sound then the cops would think its stock

Are you THAT worried about the cops... wow.
Anyways, intake definitely... I'd also suggest a cat back (to keep it legal).