[randy500]

Low side if the poa was adjusted for 134a should be about 27.5 if it wasn’t adjusted then it should be about 30(r12 setting), at 2000rpm with a big fan blowing into the Condensor.
High side will run optimally at 2.5 to 3.5 times ambient temperature.
Your not getting enough cooling because the low side pressure is too high, poa valve is not working right or adjusted wrong.
Check that your water valve is closing off the heater core properly too.
Check your vent temps with a thermometer.

Bubbles in the sight glass just means the receiver dryer is not full of liquid refrigerant. It doesn’t mean air is in the system. Your high pressure shows the pump is working and it’s somewhat charged. If it was really low on refrigerant you wouldn’t have high pressure.

You could add a little 134@, 2-4 ounces at a time, use a postal scale to weigh the can as your adding to the low side, run it a while and check pressures and vent temps, stop adding if you see better vent temps. If the vent temps don’t get better then it’s probably overcharged.