My air gauge reads 10 too high too- but only while compressing. I have a little ball valve and just close it to get purty darn accurate readings, then open it again to keep airing. I also use my front bumper as an air tank. Definitely faster with two compressors BTW.
Oh, and just to gloat, I paid $25 for each of mine- two hardmounted on little rubber feet (geyoowine Toyota parts BTW) and one for a between-vehicle floater.
Heb Dduw, heb ddim; Duw a digon
I'm that gun-totin', farm-raised, evangelical, pro-environment, OHV ridin'/drivin', Southern civil rights pro-labor Liberal yo' momma told you couldn't possibly exist.