hawaiiankine

I was just wondering if anyone has switched from a free flowing loud muffler to a nice quiet frankencar and ran it on the dyno. I just switched my exhaust (loud free flow) to frankencar cat back. I love the sound and looks of it. Need to find a dyno though somewhere. Just wondering if anyone has already ran their car and if there were any losses or gains. I have headers and not cats by the way.