PSI gages bouncing from 90 to 135psi

[Cwellc]

I have a 2010 PROSTAR w/ ISX Cummings engine. Recently had the air comp replace a year ago and recently, the main air line off the comp replaced. Now my primary and secondary air pressure gauges are bouncing around. this happens while driving not while idling, when driving the psi is normally at about 135 but it bounces from 90 to 135psi, this happens within a couple of seconds. I also replace the air dryer, the whole assembly, the governor doesn't purges until about 135psi.

any idea what can the problem be?