On the new coaches w/the 400hp engine, the air cycles up to 130#, then bleeds down to 110-115 as air is used, then back up to 130.
Try the OEM parts unit @ WRV.
I just appropriated a coupla lengths of 8" pvc pipe & glue-on end caps for assembling an air reservoir. I'll put a check valve in the air line to the chuck, then a tee 'tween the chk-valve & chuch w/a new line to the new air can under the floor @ the sofa (got 10" of headroom that isn't used for anything else, aft of the manual winch for closing the sofa slide). Two lengths of 32" next to frame rail & 36" next to slide pocket give about 15 gallons of 130# dried & filtered air. I'll drill/tap the pipe thru the end cap collar. Gotta find the pressure rating on SDR35 sewer pipe to see if it needs reinforcing.
Baja-tested '08 2-slide 36'
Alpine: The Ultimate DIY'er Project