You have it seems a vacume leak in one of the servoes that controls the air going through your climate control system. The servo that is on the driver side has two vacume lines running to it can be acessed by takeing the plastic
panel out from under the sterring wheel and from the side of the console.
It's one piece,there are a couple of servo's there under the cover to the left side of the console. The one that has two lines running to it is probally the culprit. You can look in the faq section and find out how to replace it, probally a 6 to 10 hour job or do what I did and pull one of the lines from the servo, attach a piece of tubing to the servo that you just pulled the line from and apply vacume to it. If it won't hold vacume that is the line that you work on. You cover the vacume port on the servo with a vacume cup, then on the vacume line running to it stick a golf tee or a machine bolt or what ever to keep vacume from escaping from that line. Most of the problems your describing comes from the servo that I've referenced. I belive that you would be looking for the orange vacume line going into that servo. I've ran mine like this for two years now and has worked fine, not as good as new but better than every time I got on the gas the air went some were else.
Good Luck
Poolman