i have the 04.5 with the cat and im wanting to get a straight pipe should i take only the muffler off or the muffler and cat together off

 

I'd leave the cat alone. Unless you are trying to push massive HP or desire a really loud truck, it isn't hurting anything in there.

I just deleted my muffler, I don't see a whole lot of sense in fooling with the cat.

Just my opinion.

 

I pulled mine (off road use only) and added a MBRP muffler. Even with both the stock muffler and cat gone I didn't feel a big difference in power. I'm sure it'll help with future mods. I kept the cat in the garage just in case I need to put it back on. If all you want is better sound leave the cat in place. If you want it really loud, pull it and the muffler.