I have 3inch down pipe, 3inch hiflo cat, svo y pipe with 2 1\2 exhaust to my 40 series Flowmasters. Its loud. I stand behind the car at idle and it sounds like a 5.0 liter. Has a mellow sound at 2200 rpm, nice rumble on deceleration from 4000 it sets car alarms off going down the street. I tried 3inch exhaust with 1 dynomax super turbo, it sounded all to ricey for me so i had to have it changed. my opinion flows are the way to go but, thier company is in town and my friend works there so free mufflers where the way to go