I used to get stopped all the time.
Young guy in a big car out late seems to equal a reason to be stopped.
6 times in one night is my record
Going against the popular advice, I always carried some documentation and never had an issue (over and above the hassle of being stopped that is).
When I had a loud exhaust, I also used to carry an excerpt from the construction and use regulations along with a sound pressure level meter in the glove box - that way when I got stopped I could prove my car was 2db under the legal noise limit rather than have the trouble (after the first time) of a defect notice nobody was able to sign...
I can't say it ever gave me cause for dislike or hatred of the police though.