Not really sure why you think you need an impact wrench to remove the caliper. A decent 3/8-drive ratchet and allen socket is all you need. The torque setting on the caliper pins is around 30 ft/lbs. They are quite easy to remove with a ratchet. Also, why are you trying to use a torque wrench to "remove" the caliper pins in the first place? The first rule of thumb for using a torque wrench is to NEVER use it to remove fasteners; it will take it out of calibration. Torque wrenches are only to be used for torquing down fasteners.
But if you want to use an impact wrench, you'll need an extension bar and universal joint. Not even a 3/8 impact wrench will fit straight in to line up with the caliper pins. An air ratchet may work, but that's not an impact tool.
Good luck. Please make sure the car safely lifted and solidly sitting on jack stands when doing this work.