I'm getting conflicting advise on what's causing this. If i'm on the highway the A/C on my '87 Audi 4000S blows cold. But when I come at a stand still (a stoplight for example) it starts to blow warm. Furthermore, my car has been overheating when I run with my A/C on.

Anyone have a clue?

What's probably happening is the condenser isn't cooling enough at lower vehicle speeds, which is raising system pressure and causing the high-pressure cut-out switch to kick in and disengage the compressor, but at higher speeds it cools enough, and operates normally. Pull the grille, I bet you'll find debris and some bent fins in there. As far as it overheating, my guess is that the relay that kicks the fan on is faulty, not kicking the fan into 'high' when the A/C is on. That's just a wild guess, though.