BBs, (ball bearing) as those you shoot out of a crossman air rifle. Or something similar that would fit inside the vaccuum tube to cause blockage.
This seems to look less obvious then the outright removal and plugging the end of the vaccuum line, which is illegal.
I believe the crack-prone radiator hose necks were later reenforced with a metal sleeve inside.
[This message has been edited by VA300SD (edited 02-12-2000).]