2000 5.3 Vortec Intermittent Misfire on #2 Cyl.

I have a 2000 Yukon XL with the 5.3 Vortec engine. It had been running rough and the SES light was flashing. I took it to my local repair shop where it was hooked up to their engine scanner. The code was random misfire. Further diagnosis showed that the #2 cylinder was misfiring intermittently (runs smooth, then misfires, then runs smooth again, etc). After replacing the plugs, wires, #2 coil pack and the #2 injector, it's still misfiring on #2 only. The Service Engine Soon light is also blinking off and on. Any suggestions????

bring it back and start yelling
recheck plug on #2 maybe cracked
check for loose wires to #2 coil and injector
check for intake leak or vacum leak by no 2 cylinder
do compression check on no 2 cylinder