Saab: 2000 SAAB Aero 9 5, saab aero, accelerator pedal

Question
I have two Questions: My 2000 9-5 Aero Turbo SAAB, with less than 60K miles, has a low idle and but is still the same on gas mileage. The 'Check Engine' light stays on, I took it to the dealer and they told me that I need a new 'Throttle Body', cost $700.00 parts and labor. I took it to another mechanic who told me that I need a Solenoid, which cost $40 some. What do I need?,
What is the function of a Throttle Solenoid?, How do I correct the IDLE speed?  

Answer
Pat:
 As noted in my profile, my hands on experience is limited to the earlier(Pre-1992) 900's. However, since the SAAB designs are all quite similar, I can offer the following general comments:

 I suspect the low idle is due to a malfunctioning "AIC" or automatic idle control, what you refer to as a "throttle solenoid".. This is, on most cars, a solenoid operated valve that is controlled by the main engine computer which admits a small amount of intake air(akin to a very light pressure on the accelerator  pedal)to maintain a constant idle over a wide range of conditions such as temperature, a/c loading, etc. It sounds like this is the "solenoid" that mechanic No. 2 above is referring to.
 I would go ahead with its replacement, but do a double check as follows: If there is an AUTOZONE store near you, they can do a free "check engine light" diagnosis on the spot to corroborate your earlier findings.

              Hope this helps,
                                 Jerry