Saab: Saab 9-3 rough idle, vacuum leak, accelerator pedal

Question
QUESTION: I have a 1997 Saab 9-3 and the car idles rough. Shifting from park into gear the idle drops to where it shutters and almost quits. At speed when the foot is taken off the accelerator the same thing happens not as bad. We have changed the vacuum hose and a new battery. Do you have any insights on what we should work on next?

ANSWER: I am sorry, but my hands-on experience is limited to vintage 900's (pre-1990). However, from your description, I would check the following: (a) hoses/fittings for a vacuum leak  and (b)the idle control valve

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QUESTION: Hi! My husband said I was wrong and my daughter has a 900se turbo. He drove it and it idles fine until you run the air conditioner then it dips down and almost dies. If you have the air on economy, which you know means the compressor is not kicking on it idles fine. He wanted to know if the Direct Ignition Cassette could be the problem with this. I really appreciate your help with this!

Answer
Thank you for the clarification. When energizing the a/c, which puts an extra load on the engine, the earlier SAABs provided a concurrent idle boost signal (equivalent to stepping on the accelerator pedal ever so slightly) to handle the extra load and thus maintain proper idle. Since SAAB tends toward very conservative designs, it is likely a similar methodology exists in your vehicle.Thus I would suspect a problem in the AIC (Automatic idle control) circuit. As I said, tho, I am not familiar with the details.
As to whether the Direct Ignition Cassette in any way is party to this problem, it is EXTREMELY UNLIKELY.