Lack of air flow through vents.

If all vent doors are not working properly, I would think you still have a leak or the vacuum supply is weak. Have you checked vacuum at the supply hose inside the vehicle?

I have a stupid question. I believe your vehicle has a cabin air filter. Have you checked it to make sure it isn't plugged?

I'm not at work right now, so I don't have the procedure book with me. I checked on line and there is one available for your vehicle.

I can tell you this, most GM vehicles have them located near the cowl. Open the hood. On the passenger side, between the windshield and firewall, there is a black plastic cover. Check for plastic push pins that hold it in place. Remove the pins and lift the plastic cover. Look down inside. This is where the air enters the HVAC system. There should be a filter there which is to clean the air entering the cabin much like a furnace filter in your home does.

If the filter is extremely dirty, it WILL cut down on the air supply to the fan causing low air flow in the vehicle. I don't know what made this pop into my head, but I feel it is something that should be checked.

Let me know what you find. I will be online for about another 15 minutes. If you can, let me know what you find. If I am incorrect, I can check location tomorrow for you.

Let me know.

So the plug was different and the polarity got switched? That will definately cause a problem. I have to be honest, although I know the fan would be blowing the wrong direction, I never considered that as a possible problem.

Regardless, I'm glad you got it fixed. Take care.