Headers v. manifolds
Headers are where each cylinder has it's own pipe or runner to channel the exhaust gasses down to the collector. The runners are usually around 1.5-1.75" and collectors are usually 3"
Currently you have exhaust manifolds on your truck. Manifolds are where each cylinder dumps its exhaust into the same pipe, or "log". There is one manifold on each side of your engine. The left bank and the right bank. Since virtually no vehicle comes with a true dual exhaust from the factory, they need to combine the left and right bank exhaust manifolds into a single pipe to make up the rest of the exhaust system. This is what the Y-pipe does, it literally is a "Y". On your 05 the Y-pipe also contains the two catalytic converters (one for each bank).
The stock Y-pipe on our trucks was a fairly poor design, rather than make a nice, properly manufactured "Y", they instead sort of mashed the two sides of the "Y" together, turning each pipe into a deformed oval shape and then joined that with a single 2.5" pipe called the intermediate pipe that goes in-between the Y-pipe and your muffler. All in all a pretty restrictive set up.
Long vs. shorties....
This is a huge debate and it rages on, I'll let you do your own reading on this one, but as it was explained to me, LT's tend to move exhaust gasses more quickly, so your not moving volume, so much as velocity. When a cylinder fires and exhausts, that exhaust comes out as a "pulse" and that pulse travels down the header runner with whatever velocity it was pumped out of the cylinder with, but once it reaches the collector (where all 4 runners join into one pipe) it creates a sort of vacuum in the remaining 3 runners on that bank, thus actually drawing the exhaust gasses down as each cylinder fires thereafter. And apparently LT's do this more efficiently than shorties. I would love to see this done with a smoke test, but thats how it was explained to me.
Sound:
There are lots of ways to create lots of different sounds with these trucks; muffler selection, pipe sizing, length and style of headers, cats vs. no cats, even where you dump it.
Something to consider, if you're after noise more than actual HP/TQ gains, a simple cat-back may be fine for you.
So what are you looking for? Low rumble? Raspy muscle car? Jack-ass loud?
