Borla Xr-1 (catted H) Or Flowmaster Super 10's (catted H)

I have owned 5 99-04 4.6 Gt's and have had pretty much very exhaust combo there is. Obviously the best sounding exhaust is acquired by going long tube headers, off road h or x pipe, and race style straight thru resonators vs the flow master chambered mufflers. I am a fan of the x pipe vs the h pipe because it sounds " exotic " as i call it vs the h pipes 60's/70's ol skool american muscle rumble/echo sound. If your dead set on keeping the h pipe i would go with the flows super 10's they are cheaper, will sound better with your combo. If u were running a x pipe i'd say xr-1's for sure! Also just heads up rule of thumb is on these cars 99-04 4.6 stangs that chambered mufflers like flows, magnaflow sound best paired with h pipe and straight thru resonators sound best with x pipes. Lemme know if you have any ?'s bro and and i will help out best i can .

Cheers

The Flow 10's will be louder. They are single-chamber muffs