Deleting the cats will give you HP, will delete the muffler give you HP too? If you delete both will it give more HP or would it take away HP because of the chance of loosing backpressure? Will you loose back pressure if you just straight pipe it? Sorry, I suck at exhaust systems

 

Supposedly you don't gain much from deleting the cats, except for a louder sound. THe factory muffler can be restrictive though, and you would gain power that way. Right now I am running with no muffler and just cats, and it isn't that loud, volume level is about what you would get with a Flowmaster 40 series.
Also, contrary to what is being said on here by some people, engines do not run better with back pressure. If you put on an exhaust system that is too big, you will lose power because you have lost your scavenging effects. But it goes against physics and engine theory to say that a truck runs better with backpressure. Don't believe it.

 

It'd be a dumb move on your part to delete your cats. I think you might of got the idea from the 2004 guys, some 2004s had four cats and you could delete the rear two without problems and yes it'd give you more horsepower. However if your interested in gaining horsepower through your exhaust system, you need to look at getting your y-pipe cut off and running true duals (with cats) into a Magnaflow muffler and headers with hi-perf cats.

 

"Cat-back exhaust systems are a very popular aftermarket performance enhancement. They generally use larger diameter pipe than the stock system. Good systems will have mandrel-bent turns that allow the exhaust gas to exit with as little back pressure as possible. The mufflers included in these kits are often glasspacks, again to reduce back pressure. If the system is engineered more for show than functionality, it may be tuned to enhance the lower sounds that are lacking from high-RPM low-displacement engines. No back pressure reduces low end torque but for higher top end speed... open that exhaust as much as possible" Quoted from Street Car Magazine's web site. BoB