Some of you may remember last fall, I had just bought my 99 SLE and found that when the AC was on, and you got on the accelerator, the air would change from the vents to the defrost?
Well, I didn't worry about it during the winter, but then things started warming up here in Utah.
I found out that a common problem, at least with the '99'* is that the vacuum bottle is directly under the battery tray, and sometimes acid will leak onto the vacuum line! Sure enough it was brittle and broken off. I simply took the clip off of the bottle, drilled out the broken piece, trimed off the brittle part of the vacuum line, carefully glued it back into the clip and snapped it back onto the bottle.
Presto, problem fixed! (some here said it was normal for the air to change to the defrost under a load....not so!)
A quick fix if you are having the same symptoms.