Consider this... if you plan to go for the most bang, or the best bang for the buck... well which cat-back you pick will be important. Reports are that a high flow/high temp cat with resonator (and most certainly a straight mid-pipe) in combination with a cat-back is loud. Even the Borla.

According to articles I've read on the MS RX-8, the cat-back was most designed to improve sound and the perfomance gain was gained through a high flow cat. According to MazdaManiac, your best gains are with the mid-pipe/high f/t cat.

Thus... if you want both, then you'd better pick a REAL quiet cat-back... I'd say RB or MS... or keep the stock one and change the tips. If you aren't going to drop in the mid-pipe, then anything goes and I recommend Borla or Racing Beat.

 

how much louder would the car be with a modified mid-pipe+high+flow cat. my impressions from some sounds clips it sounds almost obnoxious but that was wit the greddy sp2. how much louder would it sound with a more conservative sounding exhaust?

 

That would be exactly what I'm trying to ascertain. A couple members have said that Borla + hf/ht cat w/resonator is NG... too loud. Canzoomer said the same with GReddy instead is too loud. It has been said many times that B&B + mid-pipe is way too loud. To my knowledge the two quietest systems out there are Racing Beat and Mazdaspeed. How loud they are with the mid-pipe change... is unknown.