I don't think that the difference in vent temps on the outside vents is an indication of outside air, but you need to try to determine if this is the problem. My euro aftermarket air, which I fully expect is just like yours, has a screwy setup of the control levers. Experiment with them to see if there is any position that will give you different vent temps.

The Sanden compressor mount is quite simple. It is a mount that bolts to the lower left of the block, mounting the compressor with four bolts to the mount with two in the back and two in the front. It mounts the compressor in a solid position and uses and idler for belt adjustment.

I don't have a digital camera from which I can download to the computer, or I would take a picture of one of them. If both compressors weren't in place on these cars, I would bring one of them with it's mount to the tech session to show you, but I don't want to blow the charge on either car.