For all those with a later (post 96/97) V6 which has the additional VAC tank mounted on the set of trumpets just in front of the alternator.
Here is something to try.....
The vac tank has two pipes, a feed and an output, the fed is the one on the right or bottom (or at least should be) which connects to a large rubber elbow piece.......
Here is the test I would like you to try.....
Follow the pipe from the vac tank feed to the rear of the engine bay where it connects to the brake servo pipe (normally via a T piece).
Disconnect the pipe here and suck on it, place your tongue over the pipe and check it holds vaccum.......
Reconnect the pipe and now remove the output from the vac tank (you can do this at the front multiram solenoid if its easier).....does it hiss for a short period or not?
I suspect it will take a few days to get some responses but, there is a good reason behind this question.....which could help your economy, low rpm acceleration.....and all for under a fiver...