Toyota Repair: 95 4 Runner A/C, expansion valve, freon

Question
My daughter has a 95 4 runner that freezes up and quits blowing cold on the highway (mostly). I have changed the expansion valve and it still freezes. Do you have specs on the amount of freon and what the high side and low side on the gauges should read?
                  Thanks

Answer
The freon amount is 1.34 lbs, the normal line pressure readings with the compressor engaged are 25-38psi on the low side and 120-180 on the high side. If they are not within the specs there may be a problem with the receiver drier or the compressor, let me know what the readings are and I may be able to help more