I talked to you on AIM... but it's good to have it posted and archived too.
First off, make sure the tabs are punched out on the big nut. Put the wheel back on, and put the car on the ground, with the E-brake on and in gear. Now use a big breaker bar/ratchet (1/2" or 3/4" if you have one), and a cheater to put all your weight on it, it will come off. I have had to do this a few times, when even the impact gun won't budge the nut. For some reason it's always worse on the driver's side...
I used a half-inch 400 lb-ft impact gun, and that sucker was off in half a moment. I didn't even have to bend out the lock tab. I had more trouble getting the axle out of the knuckle.
If you have wheels with center caps, it'll be easier for you, since you can just pop those off and get at the nuts with the wheels on the ground. Then you just throw the 32mm socket on there, with a big 'ole breaker bar and a pipe on the end of it. Jump on the pipe a couple times and that thing should come loose.
air gun has always worked for me. . . . .but how much pressure are you running to the gun.... sometimes i find it necessary for the stubborn ones to crank the pressure regulator on the compressor up the whole way and wait till the compressor had reached 99.9 percent of the max psi right before it kicks off and then give that a bolt a blast with a GOOD air gun. .. . .a shot of pb blaster on it from the day before goes a long way too. . . . you are just not trying hard enough. . . it will come off it just needs more force.. . also make sure you have a nice thick impact socket on teh gun with no extensions. . . . a thinner socket, an adapter or a an extenstion on the gun will just asorb up alot of the force that is going to the bolt.... also keep your gloved hand ont he socket twisting in the direction that you want the bolt to come off ( lefty loosen) and you shoud be fine
I had to put a adapert on it to make it from a 1/2" drive to a 3/4" drive. All i could find in my box was a 32 mm 3/4" socket. Ended up just taking the socket wrench to it with a big cheater bar on it. Came off like nothing with that combo.
Learned my lession and went out and bought a 25" 1/2" drive breaker bar. Shouldn't have a problem anymore.