wierd '05 R-Edge misfire

My '05 Ranger Edge seems to have a weird misfire I am having a tough time finding the cause of. It only does it on an extended idle (red lights, traffic), at which point it will sound like a Harley. When the light turns green, the misfire will continue for about 30 seconds with some but much less than normal power output. If I hold the gas down, it will (after 30 seconds or so) return to normal and do a burnout. No meaningful codes are coming up, only misfire codes. 3.0 V6. What does this sound like?