Thanks for the helpful advice, guys. The first thing I tried was my impact gun. It wasn't up to it. That said, it's the cheapest gun I could get at HF (<$20) and I'm using a $100 pancake compressor. I picked up an old Craftsman air wrench at the pawn shop today ($18! See how cheap I am?). I'll crank up the pressure and see if that helps. If not, I'll check for the loaner tool at the parts store tomorrow after work. Failing that, I'll save it for the next timing belt change.