Air pressure too high, Can I Fix??

Hey Guys,
Picked up an o4 colubia with a 60 series, truck is in excellent condition and working hard, here is the deal, my air preassure goes to 150(toohigh!!!) b4 bleed off/ cutoff, this is how it was when i took it home, i know I should have noticed but there was alot going on at the dealer with Paper work and my head was spinning, so now what happens is the system will charge and cut out like normal, (spewwwwwshhhh) then when it falls to around 130 psi after some stabs the compresseor will start to do the machine gun thing, you know the sound, it is pumping to atmosphere instead of the tanks, my question is, is there an adjustment or does the whole valve have to be replaced, i could swear i remember a screw somewhere on all my macks and the mechanic turning it till it cutoff. A friend says there is no adjustment. Just looking for another opinion, truck is under warranty yeah its covered too (the compressor), but if it is something i can do i would rather, for the experience and not having too go to the dealer for a day. Thanks.

 

Napa like Napa auto parts? I will give them a visit wouldnt think they would have such a thing, thanks so much for your help.

 

Thanks, the people who set the truck up at the dealer seem to work backwards also, the Boy who hooked his laptop into the truck set it to 66 mph, not sure if he was joking or not, but he seemed high school age, and this is the reason i would rather fix anything in it myself, as goes for everyother piece of equipt in my yard, all the info has been helpful thanks guys.

 

Ok good I am on my way to go take a gander at everything, I wlll check popoff first, air at this point is going to tanks but after the initial fill when it falls to about 130 after some break or susp use thats when the popoff starts to flitter (sorry, for lack of better terms), no worrys i will figure it out now for sure with all the advice received here, thanks so much guys.