Update:
I ended up replacing the pressure control valve on the compressor. I had some trouble getting the compressor to turn on afterward but eventually got it going. Blows ice cold now. Thank you for your help!

215k Miles. I will try evacuating and refilling. The compressor does have a control valve and that seems like a likely culprit since the compressor is engaging, running without making any obscene noises, and yet not putting out much pressure into the high side.

I am looking at a 2013 Toyota Sienna. Blows coolish but not cold air. I connected a manifold pressure guage and got the following readings. With engine off and ~80 degrees ambient temp the pressure (on both sides) was ~85 PSI. With engine running and AC on, the compressor does engage, but the low si...