Hi, again. Anyhow, a couple ideas.
First -- down by the air hose, on the handle of the air wrench. There might be a knob. Make sure that's turned to the highest number, which is the highest torque.
Second -- Heat the lug wtih a torch, and then quick like a bunny, put the impact wrench on for several seconds. See if that helps.
Failing that, try a 25 inch breaker bar from Harbor Freight. Put the socket on, and swing the breaker bar off to the left, and press down on the end of the handle with your weight.
One time when I had a stuck on lug, I had to cut around the lug with a holesaw, 1 5/8 inch, and take the tire off that way. Remove the lug with vise grips. Yeah, sacrificed the rim, I know.