A/C Blows cool but Low Pressure is High

1999 Suburban 1500 4wd w/5.7 and rear A/C. Low pressure side is reading 45-50 psi @ 2000 rpm. Blows cool but not cold. Works great on open highway but in city feels like it is only slightly cooling the air if at all. Compressor sounds like it is running continuously. Blower inside vehicle feels inadequate on high setting. Friend has a 2001 suburban and his high setting will mess up your hair and freeze your eyes in their sockets.

Any Ideas would be appreciated.

What is the high and low side reading both at idle and at 2000 RPM?
Have you adding pure R-134a or stop leak and oil crap mixed?
Will the low side come down if you put a fan in front of rad?
Is the engine or rad getting hot?