I'd replace all the vac hoses, and dont forget the blanked off one round the back of the throttle body, then check the idle switch with a multimeter to verify that it is actually working
The wires to the throttle switch plug are round the back and they often snap! Yuo should get 5v between the pins on the engine side, and on the throttle body you should see it pass current when throttle shut, stop when throttle opened a bit, then pass current again when throttle is wide open
As for smoke I had this and it was the stem seals, would only be noticable when the engine got realy hot.
