My 05 (second owner) just would not blow enough warm or cool air through the system. The summer was the worst, I took it into an AC place and they said $1900 to $4000 to get the system back to factory standards. It just felt like the intake was blocked, I suspected some plastic jammed into the intake. Just by chance I was looking around and in the glove box was this black planel with Air Filter written on it. I opened it and there they were 2 air filters and to say they were plugged is an understatement. I just closed the door and put the panel back and started up the AC, I could use it as a hairdryer now it blows so hard. I'm going to try and find some new filters and replace them.
So if you are having poor airflow don't go to one of these "AC specalist" Open the panel, unlatch the little door and remove the 2 air filters (the second one requires a screwdriver to pull it into the door and out) then clean or buy filters.

 

https://chevroletforum.com/forum/upl...plander-41051/