Thanks jaswood - already replaced the all 6 spark plugs and the coil of the cylinder that's been misfiring. Still no go.
Then the mechanic went to do compression test on the engine and made the "head rebuild" recommendation. I'll ask about the fuel injector but my guess is that the culprit isn't there.
Thanks again!
I would first replace the fuel injector, spark plug, and ignition coil just for that cylinder as an inexpensive "trial".