Pro chamber makes the most power, but has a unique sound. Off road H will give it that MUSTANG rumble at idle, but can get obnoxiously loud if you like to put the pedal to the metal, the off road X will sound raspy and higher pitch than the H. I have had all 3......prochamber was the best but the most expensive, the H is what I run now I like it alot, but is loud at highway speeds. I installed a 12" solobaric to muffle the sound Good luck!
100% agree. I just installed this exhaust setup on my 02 GT. It is extremely loud, a bit raspy and tinny when decelerating. Working on a sounds clip also.