I Currently have BBK Shorty headers with An O/R X Pipe with weld in flowmaster mufflers. Will changing to a cat back system increase my horsepower any and by how much? Also, Will cat back sound louder than my weld in flowmaster's? And lastly what is the best sounding catback for rumble, tough sound?

 

I beleive it does increase hp. Just for the record for real performance sell your shorties and buy LT's (long tube headers).

Will it sound louder? Depends, more than likely yes, or atleast different.

Borla stingers seem like the sorta rumble tough sound you, perhaps, might be looking for.

Here's a link to some local talent.

 

well since the rest of your exhaust is 2.5 inch you need to finish it off with a catback to get the most gains, not alot but as much as you can. plus if you like the flowmasters get the american thunder cat back but if you dont you have a chance to get another one.