it's possible that it's one of those. i'd suspect, that if the rocker bolt was loose, you'd have heard a racket while stepping on the gas.

i had a collapsed lifter and bent pushrod on cyl 3 last year on my gtp, and it was misfiring, etc.... but it was a pretty easy diagnosis after i found it was cylinder 3 and it had fuel and spark there. --- while idling, i could look in the oil filler hole and see that the rocker wasnt moving!