1985 745t

okay, so I just finished replacing the hose from the intake manifold to the turbo gauge, and replaced the line that Ts off that in the dash as well. While I was at it I replaced the line from the intake manifold to taht little silver bell like thing at the top left of the fan (facing engine). I had THOUGHT the vacuum loss was the hose from teh gauge to teh manifold, but after taking it for a brief drive the turbo gauge shot back to no vacuum when I turned the car off.

I was able to hear a small leak when turning the engine off (hood open) previously and it sounded like it was coming from the vacuum line to the dash just in front of the firewall (near the brake fluid res.)... The loss is very quick, with the dash guage literally shooting right up to no vacuum when I turn the car off, so I'm thinking it should be obvious.

Is there something I'm missing here? Where might this vacuum loss be coming from? Anyone have experience tracking this down? It's not a huge issue since everything operates fine, but I would like the guage to work properly and hold vacuum. Would replacing the hoses from the throttle body to the fuel vapor collector (thats what the plastic, black cylindrical thing stamped "fuel tank" by the battery is, right?) make sense?

Any help is appreciated.

Thanks,
rt