Landyachtz

ok, so I am putting on Doug Thorley Tri-Y Headers, and a 3" X-pipe, and Dynomax Bullets, dumping off before the rear axle.

My question is, what is the fundamental difference between running cats, or going without cats.

And if I decide to go without cats, is this going to effect my engine any?

Zo6Killer

First off, what kind of car? What mods? That would help a lot with advice/info!

Landyachtz

oh whoops, sorry, its a 03 Silverado, 4.8L, its pretty much stock, other than the flowmaster muffler that came with when I bought it, and 20's

Zo6Killer

5-12hp once removed. Louder-YES. Pass emissions, NO!!! Run a straight pipe through the cats. It will then pass the emissions "mirror inspection" and if properly tuned the whole thing will pass. That's what we used to do with our GNs. If you have a welder, makes it MUCH easier to do this. Engine wise, I never experienced any problems, just improved gas mileage.

audiopro

Unless your Engine is built and tuned to run without cats, you will like suffer some performance by removing them completely. The Engine needs to have some back pressure to operate optimally.