98 Cherokee Vacuum Issues

My problem is I’m not sure if this is a problem. I have a 98 Cherokee (6cyl) and the vacuum system seems to be a little underpowered. If the engine is under load the manifold pressure drops almost down to ambient. The cruise control gets weak and the sometimes the air vents will go wonky. Ocassionally the check engine light will turn on (low absolute manifold pressure) I have replaced the MAP sensor twice.

I actually have a laptop with the OBDII interface, so I can see what’s happening with realtime sensor data. Sure enough if the engine load is 40% or higher the manifold pressure rises to 25"Hg… which at 7,000ft (where I live) is almost ambient air pressure.