I took Law Enforcement in College, so I know a little about the Highway Traffic Act. But it seems some cops don't follow it, as last year, when I was riding in the back of my friends Pontiac Sunfire (cough, I know - what a car), the cops pulled us over, because we "looked" like drug dealers with our winter toques on and loud music bumping. Next thing you know, the cops rip out the entire back seat, as they search the vehicle for weed. They didn't find anything though and just left, leaving the seat ripped up.
It really depends on the cop. Some cops will pull you over for anything - some don't give a shit, because they were like us when they were younger. One of my teachers in college actually was so cool he would tell us how to dispute traffic tickets and so forth (tricks of the trade). I know a friend of mine got $600 in fines for having the car too low, fined for his exhaust and other items on his car.
So it all depends. Just be careful

- and if a cop is behind you flicking his/her sirens, drive faster