From your very first post it almost sounds like it's a temperamental or intermittent misfire? This would lead me to believe this issue is not mechanical or the intermittent misfire is always on the edge of setting the code. For eg: a broken valve spring in which the valve normally closes but sometimes it doesn't or a cam lobe wiped where sometimes the valve doesn't quite open enough for proper combustion ??? Anyways you have eliminated broken valve spring. You could try mounting a dial indicator to your rockers and check valve opening of cyl 6 and compare to others to indicate possible worn camshaft?? While you have cover off? Or swap injector to another cylinder? Have a good lookin at injector wiring harness ? Just some ideas for ya...

 

These are the ones off of cylinder 6.

Right one is the one attached to coil. Plugs only had 2k on them.

 

I’ll try and measure the heights the valves go up compared to the others. If the same probably gonna but it back together then swap the injectors around.

 

Agree, measure the valve travel against another cylinder with a dial indicator. You could check the injector pulse from the computer with noid light. Like I said before, swapping injectors would be a good way to eliminate the injector.

 

Measured the valves and distance the everything moves. The distance is scary. All 4 cylinders are within 1 mm of each other. Cylinder 2 and 6 were same. Guess next option is put it back together and swap injectors? Any other ideas to test while I have cover off. Sorry if I sound desperate but I’m just frustrated trying to figure out misfire.

 

The lift deviation is on intake or exhaust? That might indicate a cam or lifter issue, or maybe how you're measuring.

Not much else to do, if the springs are in good shape and it appears the cam is giving you the lift you expect. Appears you're down to injector, injector wiring, and computer.

BTW, I re-read some of your thread.... plain old champions are the best plugs, supposedly the longer lasting material plugs don't work well in the 5.7.

 

Indeed, many a mystery misfire has been cured simply by changing back to good ol' copper plugs.

 

Lots of people post about having issues after putting in platinum plugs and such. Once they switch to copper plugs it seems that the issues disappear

 

So had a buddy crank engine by hand so I could measure lifters as they move. Same height as the good cylinders. So guess good sign my cam is good. So ordered 14 more plugs since I already had 2 I put in to test the cylinder that was misfiring. But figured since I’m already got half engine torn apart might as well put the recommended plugs in. Next step is swap around two of the injectors and see if misfire moves. Unless there’s something else to check for while I have the valve cover off.

 

New copper plugs in the truck. Still had misfire. Replaced all the injectors ( was only gonna swap the #6 with another but friend had a offer I couldn’t refuse of all 8 new for $150). Truck is back on road and no noticeable misfire. May have a bad passenger motor mount but least if issues. Gonna drive it around for next two days and see if issue has been resolved.