A/C Help... Out of ideas

[KDRacing]

Im going crazy trying to get my A/C working again in 2003 7.3... The system didn't have a charge in it at all when i bought it. The leak turned out to be the relief valve on the back of the compressor. I replaced the reliefe valve with an original motorcraft valve. While the system was down I also replaced the orifice tube as suggested. I Then evac'ed the system (30" hg) for about 45 minutes, and went to chrage it. I had about 35 psi on the low side and couldn't get the compressor to kick on, through trouble shooting i found that the low side switch was bad and replaced it. Now I continued to chrage the system, and it seems like its not "taking the freon out of the can" I have about a can and a half of 12oz r134a cans in it now and am reading 90 psi on the low side and 100 on the high side with the compressor off .... If i turn the compressor on and let it cycle I get normal low side readings. The compressor engages at 40 psi and is shutting off at about 22 psi, however with the compressor running the highest high side pressure i can get is around 115-125psi. Whats wrong with my ac? Im thinking the compressor? Im assuming there are 'vanes' of some sort in the compressor that would seperate the high side from the low side, maybe they are worn and allowing the two sides to equal out? Im not sure im new to A/C work.
Any help is greatly appreciated!! Have a long trip coming up next week with the stroker and were hitting around 100 degree weather

UPDATE: After letting the truck sit for about an hour, not running, with the gauges hooked up the high side and low side are now with in a few psi of each other.

[KDRacing]

Also Truck has 170k miles on it... not sure but i would assume its the original compressor

[strokemyego]

i've seen compressors cause this concern before. not on 7.3l in specific but, on regular automotive