There is nothing wrong with the P-38G in regards to yawing when either applying full power or after full power has been applied. If he's using dual throttles, it maybe an issue where he's not pushing the port engine to its fullest extent while he's doing so with the starboard engine but it's definitely not an issue with the P-38G in game.
ack-ack
I pretty much disassembled my control unit and cleaned them, re-calibrated them within AH and my problem seems to have gone away. I only noticed the yaw to the left in the G model which thinking back is strange if the problem was only in the controller. It should have happened in any aircraft.
I seldom use the rudder trim key which is different then the rudder keys “A” left rudder and the “D” key, Right rudder.
Speaking for myself, I do not have a twin throttles. Not sure what FLS has. So it was never a throttles issue.