Just watched Wheeler Dealer (bored) on the teev and they had a Thing

It was stalling because of a faulty carburettor damper

Never seen or even heard of one before?

Were they ever in Australia?
Were they ever OS? or was this some modified thing?

SU carburettors have dampers. In the UK the weather is a little damper.

Should have just googled
http://www.thesamba.com/vw/forum/viewtopic.php?t=263825&view=next 

Called a "dash pot"
The dash pot was put on carbs for emission control. When a throttle is closed quickly, CO and HC goes way up.

Dash-pots were originally fitted to our 1976 beetles, both with original 34 PICT-4 carbs.