lol mine makes that noise when i have really cleaned the inside of the exhaust i mean the whistleing noise sounds a bit like a speaker style dumpvalve hahaha!! mine doesn't make any sound when sat still have to be driving for my exhaust to make any noise!
 
Notice that I've recorded the exhaust sound at the back of the car, nearby the back box exit pipe - inside the cabin you can hardly notice any exhaust sound unless under WOT.
I'll try to record soon another sound clip inside to let you hear the difference.
 
Isnt the whistling sound the same noise as KITT when he does his turbo boost jumps in slow motion in Knightrider??


Back on topic, sounds good, mine doesnt whistle anywhere near that much! :(