Sure sounds like a vacuum leak somewhere. Check all your hoses for tears or loose connections, especially the accordion section of the intake hose and the four short runners connecting the intake plenum.
The L-jet article will probably be helpful, too:
Bosch L-jetronic Fuel Injection Idle Adjustment Diagnostic and Tune Up Technical Article Alfa Romeo Spider Specific
The L-jet article will probably be helpful, too:
Bosch L-jetronic Fuel Injection Idle Adjustment Diagnostic and Tune Up Technical Article Alfa Romeo Spider Specific