So I'm finally getting back into MK2's having had my basket case of a Jetta many years ago. Picked up a 1.8 GLI on Saturday and it's a beaut, great spec, rot free, auto (may convert to manual), few niggly jobs and a bit of paintwork correction needed but a solid rolling project for a bargain price. I've got a question on the vaccum install for the weber 32/34 DMTL, as the vaccum setup seems different on this model and I have a feeling it's affecting the dizzy advance as it's dieseling a little. I was given to understand (from memory and it's been a while) you run the servo hose vac line to the dizzy. Cap off the airbox hose, or there may have been one you run to the carb I can't quite remember 100%, remember seeing a guide but I cannot for the life of me find the thing. At the moment I've got a little switch or something mounted on the firewall, it's got a connector on it as well so I'm assuming it's powered. Top line running to the airbox, bottom line to the dizzy, the one on the side to the servo hose. Then the other airbox nub to the cold air flap. Does anyone have a diagram/ description of the correct setup or any insight into what that switch is on the firewall? I'm guessing it's to do with the pierburg 2e2 and should have been removed but whoever converted it didn't for whatever reason.
the distributor vacuum line should be connected directly to the servo hose yes, and the standard airbox vacuum line should be connected to a nipple round the back of the weber carb. 2nd nipple on the brake servo hose is capped off. the valve you mention sounds like the increased idle control valve, and has no place on a weber: https://clubgti.com/forums/index.php?threads/1-6-1-8-pierburg-2e2-carb-faq.124945/#post-1222383