Has any one punched out their cats, or replaced with high flow cats. Just curious what kind of gains you got: HP, torque, mileage etc. I have not been able to find any posts on this. Sorry if I asked a dumb noob question.

 

Unless your cats are dead, this would only result in poorer mileage and performance. Factory cats no longer pose much of a restriction like they used to, and often flow much more than stock mufflers and the rest of the exhaust system. And if the computer (via the O2 sensors) thinks that the cats are malfunctioning, it may put the vehicle into "limp home mode" or at least alter the air fuel mixture to adversely affect performance.

Replacing a failed or clogged cat with a high-flow unit (though our Jeeps have 4!) will restore performance that was lost due to the malfunction. But there's no reason to replace a working factory catalytic converter.

Not to mention the environmental impact, which I won't go into. Though it's much nicer to follow a trail rig with working cats than without. *cough*

 

Thanks for the tip! I'm just a Mustang junkie with 2 kids in car seats looking for something fun to drive and spend money on.