Boost problem with AC running

[STEAMER]

Anybody out there experienced problems with boost when the AC is on? I can accelerate with the AC on and when I get to 3rd gear and/or Overdrive my boost will sometimes go to zero. I can ease off the throttle for a second or two and re-accelerate and my boost will return to normal (3-5 psi, highway speed). I do not have any problems with boost without the AC running. From what I've researched, there isn't any vacuum being used by the AC system. Any ideas?

[BobND]

The vacuum pump is driven off of the backside of the serpentine belt, on the "downside" of the AC compressor.

If, for some reason, the outside of the belt is glazed, the tensioner is not working properly, or the belt is a size too long, perhaps the belt could slip, and not adequately drive the vacuum pump.

[Barry Nave]

This issue and others was the reson I went with the Turbo Master. Once I've done all I could to restore elect,vac boost short of R&R the ECM it was time for a change.