P0304 code -Tried many things, Still Puzzled!

[2005_Denali]

I have a 2005 Envoy Denali 5.3L with 120K miles, was driving fine then all of a sudden it had rough idle, shakes, shudders, jerking and check engine light flashing. It threw a code P0304 (misfire #4 cylinder).
Here's the steps I took so far:
Bought new coil packs, switched injectors, tested injector wires and plugs, changed spark plugs and wires, checked vacuum lines, cleaned throttle body, cleaned MAF sensor with correct cleaner, regularly use fuel system cleaner, disconnected battery and run compression test.
I'm at a loss for what to do next. I have had a lifter tick for about a month but still ran fine, could the lifters got worse and be causing these new issues. Also ONLY #4 cylinder spark plug smells like fuel & looks slightly damp. The other spark plugs are fine.
Please help on what to do next, I'm puzzled. This has been a long 4 days of stress and I need this fixed asap.

 

[Ackbobby]

What's the pressure going into the sleeve ,also have you a different weight oil recently? Air hole some where ?crack in block? Did the spark plugs get gaffed properly or maybe lifter it self could be fouling it up just enough to piss it off...gasket problem just some ideas nothing big ...maybe if you redo it again from scratch (just incase u had missed anything)....http://youtu.be/DjL_Wefla0s
Maybe this video might help