I'm having a dual 3" exhaust down. muffler size may prove to be a problem for ground clearance. i've been looking at Dynomax Bullet mufflers, which are a designated race only muffler, but they're small, 4" round. The Ultra Flow's come in round, but 6", or they have rectangular cases whith are 4" x 9".

I have 2 3" CATS that I will be putting on, I'm just wondering how much this will quiet an exhaust down, for anybody that has an A/M exhaust and kept the cats, or removed the cats and noticed a difference. I am running a 230/234 dur. cam...

 

The difference in my system (bullet muffler with no cat) is enormous with the cat in there. With it in there you can stand behind the car and rev it up and be like "damn that's loud"

But with the cat out, stand back there and rev it up. It gets so loud it's white noise to the point that you can't physically hear it get any louder.

So yeah, it's a big difference.