A/C Not working properly.

I have an 1989 Chevrolet s-10 Blazer 4.3 6 cylinder 249,000 miles. The problem I have is that the a/c turned on at idle really sucks and it works a little better on the highway but not really. At first I thought it was an overheating problem but the truck never really overheated and I changed my radiator, waterpump, thermostat, lower and upper hoses, fan, and the fan clutch. Still the same. I then changed my a/c compressor with the clutch and my accumulator including my fan mtor as well. Still the same. The evaporator canister gets cold and sweats but after a while of running the ac on there is still moderate air coming through the dash. The compressor turns on fine since it is new. There are no leaks in the system. The trucks heat at idle reaches a temperature of 200 degrees. This truck is kept in really good condition and well taken care of. Please help me with this problem.