#3 misfire, injector change no help

[clys]

Hey guys, I've got an '08 here with a P0303 #3 misfire and contribution for the same hole. It runs smooth when first fired up and while driving, but after you get it warm and put it in park (still running) it starts to buck and cyl.3 is dropping right off on the power balance. I changed the injector and still nothing, #3 shows an 8% deviance on the relative compression test and there is a lot of blow by. I know that cyl.3 IS low on compression but why does it run so smooth when cold then drop off when warm? Is the ECU seeing that it has low contribution and cutting the injector to prevent more damage? This one is confusing me, any help would be appreciated.

[sinner6.0L]

what do your short fuel trims look like on that hole? that should give you some indictation of what the pcm is doing to compensate