https://www.mojotiretools.com/N2_FAQ_Q01_files/image004.gif Air from a 150psi pump and nitrogen seem the same, dry air must be under one of these, but there isn't a difference. The difference is from water in the air from what i can see, n2 and o2 are diatomic molecules, and iirc statistical mechanics would say that it wouldn't be until the 3rd term there would be differences in pressure. as far as leaking through the tire, i can believe that one.