General Maintenance & Repairs - Ac air blows out all vents need help

My 99 trans am blows air put of all vents when on max ac or regular ac. When on max ac I can I can still feel air blowing barely on my feet and air barely through the defroster. Ive checked all vacuums and everything seems fine. Any ideas? This isn't the usual line came off the back of the intake or the three way check valve and it's driving me insane. The car has a bigger cam though but all my buddy's ls1s with big cams don't do this so I'm stumped. Any advice would be appreciated.

Anybody?

There is a vacuum line off the back off the intake manifold (thin hard plastic) that supplies vacuum for the vent controls. Make sure that has not been pulled loose. Should see it around where your PCM is under the hood.

I already checked that and it was fine

Check the wiring in that area as well to make sure it is not damaged.

this is going to sound ridiculus and I woudn't have mentioned it if it hadn't happened to me. I had an 84 and the air would barely blow and we could never figure out why. finally one day I was doing some stereo work on it with a buddy and he was up under the dash and found a plastic grocery bag wedged way up under dash that was blocking the intake for the air therefore not pushing any air through the system. pulled it out, laughed about it, threw it in the garbage and the air worked like they day it was bought. I have no idea if a newer system has the same type of intake but I figure I would mention it.