pricing around the net sellers, I've explored a few others and Phil is always the best price.
If your car has the Servo ACC system, interestingly this system was originally designed for the Chrysler Imperial back in the 60's and Mercedes bought the patent for it, why I'll never know. If your car is equipped with the heating servo, and it goes, I had mine fixed by Performance Analysis in Tenn,. better then new.

Good luck with the cold idle. I would have it check by a good mechanic who knows these cars, as you can spend a lot of money and in my case it was just a few adjustments and I saved quite a bit of $$ rather then replacing parts. I am lucky the shop I go to with my daily driver a 99 C280 and the project 45SLC, was trained by Mercedes and worked for them for 10 years or so and also BMW trained and worked for them for 5 years. Only downside, he as most smaller one owner two or 3 mechanics can't afford the diagnostic machines you need today but for routine service, suspension work, and even check engine light work, the shop I use is very good and his labor rate is $50 per hour instead of $95 an hour at Mercedes.

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Al Lueb
1999 C280 54K miles
1979 450 SLC 144K miles