2e2 troubles

You need to check a few things. Do you have a multimeter? If so check that the connector that goes onto the TTV (item 38 in the exploded diagram above) gets 12V between it's pins (unplug it to measure) when the ignition is turned on.

If that's OK you need to look at the actuator/pushrod of the 3-point unit, this is on item 40 above, it's low down at the rear of the carb on the driver's side. The part that sticks out towards the front of the car is the actuator/pushrod. When the car first starts from cold, for the first 2-20 seconds or so, depending on the outside temperature, that pushrod will be sticking out maybe 15mm, then it will withdraw, partially to about 8 or 9mm extension. For about the next 5 minutes after this partial withdrawal, this pushrod will not be touching a grubscrew that pokes through a right-angle bracket nearer the front of the carb. Don't adjust this grubscrew!

After that 5 or 6 minutes this screw should come into contact with the end of the pushrod, it's the bracket/screw that moves toward the pushrod. Give it 10 minutes to be sure what's happening/not happening. Again, don't adjust this grubscrew!
If it isn't touching after this time, there's a very strong chance your waxstat is dying or dead. Very common age-related failure, but not too expensive, or difficult to replace (GSF do them). Also known as "Expansion element". (Item 41, above). The waxstat, when working OK, is intended to keep the revs a little higher than normal idle, during these first few minutes, decreasing them as it warms up, down to the 'normal' idle speed. Don't try to move the grubscrew to compensate for the sick waxstat, it won't be a good thing.

As far as the rev change with connecting/disconnecting the vacuum reservoir, not sure, but you haven't convinced me that you've checked/tested the pull-down unit as OK yet, so do that, 'cos it's connected to that pipe. You've got to be methodical and rule out one thing after another.