Were there different engines in the 04? How do I know what my engine is? Will I gain anything by removing the Cat?

 

On the drivers side of the engine on the valve cover there is a tag that tells what hp your truck is, many diiferent opinions on the cat removal, I couldn't tell a lot when mine fell off but I think over time they might start to plug and be restrictive.

 

Here's a link to a thread that talks about the cat issue in detail.
https://www.dieseltruckresource.com/...threadid=51550

 

Until the truck has I believe 100k on it, the cat is covered under warranty. If it gets clogged up (which it will), just have them replace it under warranty. A non-clogged cat isn't going to be a big restriction, and if it's under warranty it's their problem. Plus, they might be able to say gutting the cat caused some other engine problem should you need them to, say, rebuild the motor in the thing.

Once the warranty is up, gut it and if you really want to be through, put a straight pipe through the housing. This way you'll still pass visual inspection (hey! He's got a cat there!), and the straight pipe through the cat will give a slight performance advantage because the exhaust gasses don't expand (slow down) and then have to compress again (speed up).