Shorty headers are better at low end torque, and long tubes are better at higher RPMs. A X pipe is more effective than a H pipe. You get better scavenging from a X pipe. Shorty headers will also fit where the exhaust manifolds are now, and long tubes will need to be custom fitted. In other words, long tubes have a flange welded into the exhaust pipe. As for coatings, they all ware off in time, and stainless headers will turn blue in time. That being said, I have summit shortys on my 97 vortec. The thing to do is to strip off the OE black paint, and repaint them with VHT header paint. Follow the directions on the can. Do this before you install them. I just let the paint burn off of mine, and repainted them on the truck, that years ago, and they still look good. As for obstructions, or restrictions, well the OE exhaust is restrictive. This is in the cats, and the muffler. A set of high flow cats, and a good muffler, that flows will be a big help in removing restrictions. Keep in mind that Flow masters are restrictive. Any muffler that has baffolds in them will restrict flow. You need a muffler that you can hold up to the light, and see straight through. Magnaflow, Borla, SLP, even old school glass packs are not restrictive. You can hold those mufflers up, and look straight through them. None of this will give you huge performance gains, but is a step in the rite direction. As for exhaust pipe size, well you are good to about 350 to 400 HP range with the stock pipe most likely, Is your truck a vortec ? if so a dual exhaust is easy to do on these trucks. 2 pipes into 1 muffler, just remove the muffler. and replace with 2 free flowing mufflers.
