I got flowmasters 40s on now.Thinking about getting some mac pro dumps. Besides being louder is there much of a hp gain.

 

I did the same move, i went from flows the original 40's dumped, to mac pro dumps, and mac is way better, it sounds better more tone and I also gained more low end tq, and I gained or felt more of a gain than w/ flows, imo flows suck, mac pro dumps out flow them and are louder. louder at idle and at wot