1987 190DT A/C Issues

[BSharp]

I cannot figure out ths a/c problem. I bought this car a few months ago so I do not the history. It has a R134a compatible compressor (has a label on the side). It has a R134a retrofit sticker on the rad support. It has a R12 fitting on the low side line and on the compressor. It has built on R134a fitting on the condenser. I cleaned the condenser, new fan clutch and wired both the aux fans so the run when the compressor is on. Hi side @ 1500 rpm is 280 and low side is 30 psi. The temp at the vents will not get below 70 F at highway speeds. At idle it is the high 80's. The HVAC pods are working, I can disconnect the compressor and the the system will blow ambient temp so I do not think the heater is bleeding air. I am pretty sure it has R134a and the numbers are a little low but it should cool better that this. The low side line does not seem to be overly cool. I know R134 does not work as well as R12 but it should be better than this. Any other ideas on what to check?

Another question concerning the HVAC controls (aka Rubiks cube of the HVAC world). To get maximum cooling the center vents are closed and the a/c comes out the side vents? If I open the center vents slighty warmer air will come out.