Previous owner said he had replaced the gasket at the expansion block and then topped up the system - no vacuum or gauges.
I have added more R-134a AC Pro (with stop leak.) At idle.
Without a tach, I don't have a reliable way to hold 2000RPM, but I am working on that.
I also felt like the valve was not sealing in the port, which I read on this forum that they all leak some. I found a cap and screwed it on tight.
For more than 2 years, the behavior has stayed the same. At MAX settings, my vent temp is below 40F. If I bump the temperature control up just a tiny bit, my vent temp is in the 60's.

I would prefer to be able to moderate the temperature rather than feeling like stepping from a freezer to the desert.
I believe I can borrow a set of gauges and possibly a vacuum pump.

With the grand-kids on board this is more important that if it were me by myself.