Originally Posted by ghunt

There's a BIG difference in sound between cats and no cats. The cats do block a lot of sound and that's how people get away with muffler deletes on otherwise stock cars. Once you pitch those cats though, you really need some kinda muffling on there or it just sounds obnoxious. I ran my car for one day with an off road prochamber and could not believe how much louder it was than with high flow cats even.