well, i developed a miss this weekend on the parkway, this clicking sound under load(on my old 2.8 it happened and now my 3.4), not as much at wot,where the more gas i gave it, the slower i went and the car shook and the tach jumped all over, and it overheated(not too bad) i pulled over, let it cool off, and what to ya know, sounds like a lawn mower, #6 dead cylinder.Pulled the #6 plug wire off at the dizzy and it was arching to the wire, so i have spark. i suspected a fuel rail clog, nope, so i tossed on one of my old 2.8 injectors to see if the miss went away, NO it did not. Im going to check injector niod when i get a chance, and other than compression and injector niod, what else should i check, i think the sound is fuel injectors, b/c it did it on my old motor, and now the egr isnt hooked up,though it makes the clicking noise while drive just fine since i bought it
it sputters and tach jumps everywhere under a good amount of load, like when i floor it in 5th gear, or go up a steep hill in 4th or 5th, and the tach jumps at little bit on bumps, like the seams in the highway, the dizzy was rebuilt about a month ago, and all the ignition stuff is new, and i have a jegs 49,000 volt coil. im lost, all of my ignition is new, fuel is good, im about to let my boss at my work have it, cause he's the man, and my head has exploded trying to figure this out.

 

Since the tach is jumping, I wonder if this is an rpm sensor issue. Your best bet would be to get a hold of a scope (I use a Fluke 98) and see what the "shark fin" looks like on the secondary side of the ignition coil. But if you wanna go the guessing route, try swapping out ignition components such as ESC, rpm sensor (GM doesnt call it this), ecm....