Giving credit where it is due, all that good advice came from pinkmg, aka Mark.
But since you asked, there should be a hose between the air cleaner and the PCV (Positive Crankcase Ventilation) valve normally on the top of the valve cover. That’s the PCV hose.
Here’s a good lesson on using vacuum gauges from the Second Chance Garage:
And for VW’s with dual carbs (and I guess anyone with dual carbs):
http://www.aircooled.net is a great technical source for VWs.
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster
If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)