I had a Silverado 4.3 would not run on after market wires. I also worked on a buddies S10/4.3 that ran rough all the time. He replaced everything, even the intake manifold gasket. I looked it over and suggested buying GM. He said he didn't care how much it cost, he was so sick of messing with it. He replaced the cap rotor and wires and it ran perfect. I know people will say that with newer vehicles troubleshoot and replace only the one bad wire with oem.
The wires I bought and the ones he bought were not cheap, they were the good ones.
Don't do this on what I'm saying, have it checked out, I dont want you to waste your money with my internet evaluation but it is something to consider.
Also try searching for that problem and aftermarket wires, I think I found others saying the same thing.
http://www.gm-trucks.com/forums/topic/66081-random-misfire-on-5-8-running-rough/http://www.tahoeyukonforum.com/forum/showthread.php?t=30308
