Just thought I would share a simple discovery. Replaced my heater core today and noticed the vent door that moves with the "hot,cold" lever wasn't closing all the way when the lever was pushed all the way to "cold", meaning some hot air from the heater core would be allowed to pass through the door and through the vents into the car, even though the lever was all the way to "cold". So, if I was running the a/c it would have some hot air mixed with it. I'm certain this is why I could never get my last Camaro to blow cold enough a/c.

I sprayed some silicone lube all over the cable that moves the little vent door open/closed and now the door closes completely with ease and with no adjustment of the lever itself. You should be able to access this point on the cable by removing the passenger under-dash panel, without removing any other dash parts.

 

Nice job of pointing out the tips and tricks!!!