Monroe air shocks

So I've gotten 3 sets for my duster over a year . They all leak down . They all claim 80-150 psi . No shops I've been to , my compressor , no gas station can get 150 psi to end of the line to even come close to 150 psi .

Why do they make them 80-150 if 150 is not actually possible ? I need air shocks to get me clearance for my 275/60/15 to clear so if they aren't at least half way jacked up they hit