Vaccum Leak or Ac Problems?

My ac blows cold, but when I give it gas it's like i have the heat on, then when i stop at a red light it blows cold again. Someone said it could be a vaccum leak but i've had the vaccum system checked twice. Any Help?

It sounds like a vacuum leak. Check all of the vacuum connections under the dash (there are 3 vacuum motors and the control assembly to check). The problem could also be low engine vacuum, which could occur if the engine has a misfire. Also check the orb attached to the side of the evap housing, under the hood, for vacuum leaks, and make sure the engine vacuum source is the tap on the intake manifold between the carb and distributor.