I have me this 08 Sierra with the 6.2L, it has an intermittent misfire on cylinder 5 at idle that dissapears while driving that I CANNOT find the reason to. So far I have replaced the injector, coil, spark plug wire, spark plug, and pushrods all for that cylinder. Fuel pressure is 43 psi at idle which is fine according to the service manual (Please tell me if that's incorrect). And I've noticed both banks like to run slightly lean (1-3%) with bank 1 running slightly leaner (About 2-4% leaner). I've already checked and replaced all the vacuum lines I could find and even the intake manifold gasket along with the exhaust manifold gasket. This really has got me stumped so any help or ideas would be much appreciated, please let me know of you need more info and thank you for reading!