I've had no problem getting mine off I've have a small 35 gallon and 80 gallon compressor, the 35 pushing 125 Psi and the 80 anywhere between 90-120. I've used my craftsman one rated at 600lbs and my Carquest rated at 1000lbs with a 2 inch anvil so it around 800lbs if not 750. Usually it the compressor that can't keep up with the impact cfm. The hardest one I've messed with was a van and it took even a while to get that one off. Back and corny little at a time with pb blaster till it came off. How much did you pay from the the compressor and impact? I'm asking because you could of bought the IR cordless impact 20v that has 1250lbs, and its crazy powerfull for a 1/2 cordless impact.

 

I don't disagree with any of the above. I've bought some "Evercraft" stuff from Napa. I'm not sayen it's better than others, but free replacement and they are everywhere. Squirt it , heat it, (even slowly pouring a pot of boiling water over it), Then with both feet, or a cheater bar give it all you got, it should go. "commit to it" give it all you got! Get a breaker bar that you can't break! oh, lefty Lucy of course.

 

mine came off easy with a 1/2" impact.

 

I never said it wouldn't come off with an impact, but obviously the OP said his isn't...

 

I've ran into this problem many times now. Best thing that worked for me is 3/4 in. Drive set. They got it at harbor freight for cheap and you can always return it