Does anyone know the purpose of the little screw between the progression hole cover and the idle adjustment screw on a Weber 40 DCOE 28? (Pic below, two per carb) It's not in any of the parts diagrams I've been able to find, though it does appear in online photos of '28s. It also is shown in a drawing in the owners manual, so I believe this is original to the car (1971 Giulia 1300 Super). From the position I'd guess something to do with the cold-start circuit. There appears to be a drilled hole, suggesting some sort of air bleed, but that seems like a pretty dirty place from which to be drawing air. Anybody know?