Suction Jet Pump

[saabman]

Ive been around my engine bay for a point where I can get a low vacuum.

On the air box is a nipple which would be ideal but the pipe goes to the "suction Jet pump" which is part of the brake booster vacuum circuit.

What on earth does it do? it looks like a venturi but why, how and what for?

Its item 7 in the attached drawing