sounds like the copper had taken a couple of viagra, wanted to show how hard he was, prick!!!!
there is a legal sound limit on car exhausts so perhaps having it tested and a certificate to prove its loudness might not help in this case. The nismo exhaust is illegal, hence the reason why it wasn't a official option through nissan.
some past stuff on loudness here
http://www.350z-uk.com/forum/viewtopic ... c&start=15