Blocking vacuum pipes, not running in idle

[haaren]

I wanted to see how the engine would react if I block all vacuum pipes, blocked all pipes on plenum except for the brake servo off course. Only the hose of petrol flume filter I blocked, the other hoses are to the open air.
The engine will not run idle anymore, a bit strange so I checked all again and all is fine. Because it was a test I decided to take it for a short spin, with declaration it has some louder plops as usual but the most important thing it doesn't shunt with low refs / speed. When returning to my house it's trying to keep idle but the revs are between 400 en 1000rpm, it wants to stall but then quickly rev up. To be sure on my experience I mounted all pipes back as original, direct the engine runs normal idle again, take it for a spin and the shunting is back as well...
So experiment was a succes but now I want to know why it doesn't run idle when blanking off the vacuum pipes on plenum, does someone have more experience with this as of course I want to blank off all vacuum pipes to get rid of the shunting.
Thank you

[PabloGee]

Assuming you’ve found the “goddamn shunt is killing me” thread on here?

The shunt can be a few things, but the idea in that thread is that it’s to do with advance timing.

Might be time for a smoke test too, which could cause erratic idle.