Engine misses only at idle

Im having a problem finding out what's wrong with my truck. It has a miss on cylinder 2 after the engine warms up but only at idle. I've replaced w the factory den so twin ground plugs. Put new plug wires on. Swapped coils to see if the miss followed and it stayed on cylinder 2 so not a coil prob. I replaced the injector on cyl 2 and its still missing. Has a knocking sound too. It runs fine when under power the miss goes away till back at idle. Its noticeable from 750 rpm to bout 1000 n clears up. N fuel milage has went down. Nobody got any ideas what it might b? Burnt valve maybe?

 

Did you ever figure out what this was? My truck dies this too. I am freaking stumped.

 

With what you have done, a compression check would be next.