How much air do you use?

i just finished hooking all my stuff up. With 1/2 air lines and valves, 145 psi pressure switch, and 6 gallon tank. One hit when i put everything up sucks from 145 psi down to around 90 or lower. Does that seem right. My compressor is on all the dam time, blitzlift 337 is what i have. It doesnt seem right what does everyone elses do? A solution maybe to my problem would be cool to.