No power to 930 vacuum switch

[Marshall Deems]

I have a low idle problem at cold start. After the car warms up, it operates perfectly. The car starts immediately upon cranking the starter and until my 45,000 mile service was performed last week, the idle went from 1100 rpm to 950 rpm in about thirty seconds. Perfecto!

Now it just puts around 600 rpm for minuutes gradually rising to the 950. My research showed that there was no power going to the electric switch beneath the intercooler thus allowing vacuum to advance or retard the timing.(not sure which). If I disconnect the blue hose from the distributor, the idle is fine.(no vacuum) When the car is warm, it will idle too high if I pull off the line. My wrench told me that the power to the switch comes from the box brain under the seat. But what tells the box to send the current to the switch? Ox sensor is disconnected and car seems to be tuned perfectly at operating temp. It just seems funny that the cold start problem occured immediately upon the completion of the service. Loose wire? He suggests not.