no stepper-motor type controller, rather more like an electric choke. this is another possible culprit, that dadburned 'auxiliary air valve' in Zu parlance:

I believe that was the source of my idle trouble - was stuck shut at start up, when it should be open to provide bypass for high idle. and if either of the large vac hoses to this thing are not seated right you will get poopy idle & running, as it is a fairly large unmetered vac leak.

just like the ECU temp sensor, it is buried almost beyond accessibility. <img src="/forums/images/graemlins/angry.gif" alt="" />