After driving truck for 10 - 15 minutes the check engine lite come on and almost all power is gone. It it gave code for misfire #6 cylinder. Sorry working on 3.5 liter. Swapped plugs and cop with #5. Drove again, same thing come back it says #3 misfire. It’s different cylinder almost every time . Replaced plugs and cop to motorcraft. No difference. Any ideas?

 

Code p304 p306 p068