Miss in Cylinder 8

My 97 Silverado is missing in cylinder #8. It gets worse when the engine is warm and under a load (accelerating) between 1200 and 1600 rpm. The intake gaskets were changed in March. This started just before the fuel pump went out. I have changed the plugs, wires, dist. cap and roter. the fuel pump and filter. The diagnostic code always indicates cylinder #8 missing, and it backfires a little at higher RPM's. Any ideas will be appreciated.

My 98 has this problem on cyl 6. It was diag by GM as a mechanical sticking in the head. I have been living with it as it uses no oil, mpg good. Just aggravating as hell sometimes going up steep hill or hauling stuff

Valve sticking?

Well, they said mechanical sticking in the head. Not much else moving up and down. Mechanic also said the 5.7 has problems in this area( sticking valves). They have seen it before, many times. Funny mine started about the same time I noticed the orange crud around the heater hose on the intake manifold. If I would have only known that that is an early sign of manifold gasket failure!!! I did my own intake gasket for $40 and a days labor. FYI, dealer diag my missing for free after I told them all I had done in a written report. :2cents: