WOW, whistles like madness now. unless you REALLY like whistle like i do, id stay away from the ats/WW combo. it is SOOO loud. i love it though. no more surge, truck seams to have a bunch more power, thinking maybe i had a leaky up pipe boot. some day my leveling kit will show up and i can put on my new 20's and ill be set for a little while. time to save up for some injectors.