Chevrolet Repair: 99 chev p/u 4.3 v-6, throttle position sensor, laser temp

Question
a/c seems weak, but has correct level of refrig in it and blower motor is a-ok? only other thing 'bout the system is that the selector mechanism that sends the air to the different places(defroster, face, foot, etc..) is only really working on the face selection and a lil bit in the defroster position. laser temp reader says it is producing 49-50 degrees out the vent (in the shade, and at idle) any ideas? also, my engine rpm's surge about 300-400 rpm when trying to hold a steady 45-65 mph's, but not when i am at about 65-75mph. any ideas?  i have 2 new cat's and 1 new o2 sensor(bank 1 position 2), new fuel filter/cap/rotor/throttle position sensor. abs sys not functioning & disconnected.


Answer
Hi Mark,
Sounds like a mode door, which controls where the air flows in the a/c system is not operating properly. That will allow more air than desirable to pass thru the heater core.
I assume you checked the fuses?
See if the door lever above and to the right of the gas pedal is operating.

Check and clean the EGR valve.

Van