I.R Is the way to go. but for home use ..chicago pnu.cp-734 is great, bout 425 ft lbs of torque and a fast hammer .the thing about air impacts is ,alot of torque does no good with a slow hammer gun.the cp and Ir have fast hammers. snap on and the cheaper blue point are slower and parts can be difficult to get.you can rebuild the c.p for about 15 bucks and the i.r not a whole lot more plus parts are easy to find.I did exhaust and brakes every day for 13 yrs and beat up alot of guns .many way overrated and over priced .the mac razor back was a beast also.
matt