The compressor is only half of it. There are a lot of very weak pathetic pneumatic impact wrenches out there. One of the best ones on the market it the Proto J150WP that has 1260 foot pounds of breakaway torque. Cost is $334.78 on Amazon. Don't just buy the brand, because even Proto, Snap-On, and Mac all put out cheap ones also.
Proto 1/2" impact clickyI bought a new 18V DeWalt and it won't break loose the lugs on my pick-up truck. I still use a 30" pipe on the breaker bar. I was even more disappointed in the DeWalt when it wouldn't break loose the 1/2" track bolts on my Nodwell below.
When you buy either an electric or pneumatic impact, try it right away so that you might be able to take it back if it doesn't work for you.
Bill