99 burban A/C issue

Alright this beast has front and rear A/C the rear blows a little cold but the front is only slightly cold. I've replaced the Orifice tube and it seemed to get a little better as far as temperature goes. I flushed the system with A/C system flush. I can only get about 1.5 12oz. cans of 134a into the system before it reads full charge. I've also removed the front evaporator and cleaned out the fins for better flow through the ducts. The outside temp was 98*F the duct temp was around 75*front and 68* rear. what would cause the front not to cool the same as the rear. I've attatched a diagram of the system, maybe someone can figure it out better than me......Thanks guys

http://s37.photobucket.com/albums/e73/aircrewman/?action=view&current=aclayout.jpg

The low pressure side reads in the blue on the advance auto parts pressure gauge, I haven't read the high side at all. when you drive the vehicle the rear blows cold for about 10 minutes or so then both front and rear blow warm. after parking the vehicle and letting it idle the gauge reads in the yellow. ?????

u said you removed and cleaned the evaporator? i'm asuming you meant condenser. What u need to do is replace the evaporator, its normally in the engine compartment near the cab. go ahead and replace the orafice tube again, then put in 3 12oz cans of freon. the evporator is clogged and is causing your issuses.

I had the same problem and I added more 134a alittle at a time untill the front vents blew cold.

also if you didn't pull a vacumn on the system then your gonna have to vent the high side to get more freon in

Check this place out for AC problems. Pressure readings are a bare minimum for any help.

http://acsource.net/acforum/

reciever drier desicant bag is probably ruptured and debris is floating around and clogging up the system.if you are going to replace the evaporator make sure you replace th reciever drier and the orifice tube and remove as much of this junk as possible by flushing out the system thoroughly. exwldr........