i believe you are referring to a check valve on the line, that is there so that the brake booster isnt "drawing" vacuum constantly when you arent using the brakes....often the old ones are shot, and you can blow/suck air through them freely....should only go one way.......as far as the exact routing of where the vac lines take their vacuum pressure from, this is less important.....as long as everything still gets vacuum.....if there is a check valve on a vac line connector on this new line of yours, then this is so that if there was a vacuum leak, it would not constanly drain pressure from the system.....a good thing.....

You can test whether the fuel screen is plugged or not by swapping output and return lines on a full fuel tank and seeing if the flow improves. If it does, screen is probably clogged.
I have a thread on how to drain the fuel tank with very little effort using the return line.

Main vacuum line should have a check valve on one of the branches.

Appreciated Justin. Thank you.

Thanks Kerry!

I replaced to inline filter, the main vacuum booster supply hose, and the 3-way anf 4-way T-fittings today. (The old filter was definitely dirty). Unfortunately not too much improvement overall.

Your description of it driving like a non-turbo may be very descriptive of my problem.

I am not clear on how to test the overboost line. It's a rigid line and I'm afraid I will break it if I try to remove it from the ALDA fitting. Visually it does not appear to be dirty or gunked up in this particular section. It does terminate into a 1" rubber tube before attaching to the firewall (switch), but even reach that 1" rubber may be a challaenge. Anyhow, are there other points or ways to test this? Again, I am pretty sure that the turbo is not working at all :-\

Thanks.

Before you disturb any of the lines, remove the banjo bolt from the back of the intake manifold and make sure it is clean. You should be able to blow air from that fitting to the banjo fitting on the ALDA with the engine turned off.