I never messed with the pre-set pressure, but the regulator is adjustable just like any compressor regulator. It comes pre-set at 65psi which is max recommended braking pressure IIRC but I think the little compressor will make 100 maybe?
I just tee'd off the line from the reg to the exhaust valve and put a brass valve on it with a coiled air hose. When I need to use the air hose, fire up the truck, engage the exhaust brake and when you start using air it triggers the compressor to come on (and pulls air away from the brake).
There' about a 0.1% chance it would fill a truck tire. I think I've hit the maybe thermal overload on the compressor a few times if I use the exhaust brake on/off repeatedly dozens of times like on a switchback road.