I did this same thing on my street Audi when changing the timing belt. Went to the local Audi dealer and asked, very nicely, how they did it. I was told to heat the Sh*t out of the bolt and take a 3/4 inch breaker with a pipe and give it all I have. Brute Force and Ignorance was the name of the game. Since then I have probably had the street car pulley off a half dozen times and my race car about a dozen with no problems. For me MAP gas works fine and I just happen to have a 3/4 inch socket set. 1/2 just will not cut it. BTW I was told by the Audi tech that a 1/2 impact wrench, no matter the lb/ft, will not take off the crank pulley.