Removing Cats From Exhaust

[Old School]

And honestly, why wouldn't you run a cat?
I ain't no environmentalist, I dislike most of those folks. But running cats on a virtually stock car is a tiny loss in power.
And they clean up the exhaust by some 90% or something.

Heat. Cats basically double the exhaust temp. You can see this by taking temp readings, with an IR thermometer, just before and after the cat. Removing the cats results in reduced interior temps and vastly reduced sill temps.