Newbie to AF and an engine stalling problem

I just bought my first Golf recently and it's a really nice drive. It's a 1991 Golf J-reg Driver 1595cc. Really smooth running and has caused me very few problems except this one..:

My Golf likes to stall and produce really low revs when changing gears. I have to keep my foot on the throttle to keep the revs up. I had a full service done only 2 months ago.

It's happened a lot recently and having trawled through the posts about Golfs stalling on this board, all the useful replies point to a number of problems it could be:

1. Temp gague not working, never registers any temperature.
2. Air inlet tube cracked, it's been cracked in the past but the engine never stalled.

So with both of these faults, could a dirty carburettor or is my air intake valve not working exerberate the problem? Or maybe something else?

There should be an idle stabilizer valve right in front of the valve cover, remove & clean out with throttle body cleaner. It might be good to also clean the throttle valve.