Greg, If I recall, there was an instruction with my leakdown tester to allow some margin between tank pressure and your regulator setting. Since I have a 100 psi max unit, that meant I had to set my regulator to 90 psi (and do MATH to figure out my percentage loss!). I'm not sure how much my reading would have been affected with a higher regulator setting, but I thought I'd throw that out there for you to consider. Rob