pull the spark plugs and squirt a little bit of oil in each cylinder
if the plugs look bad put new ones in it

see if that helps the compression issue, it should get up to top compression in just a couple of revolutions, the oil will help loosen up the rings that are probably stuck from sitting.

check the air filter also, try cranking it without it and see if that makes any difference.

We did that and got 130 to 150 PSI. It did take quite a few revs to get to max though.

Run a compression check. Valves tend to get sticky when the truck sits.