What is the function of the central plug (#71 on the attached drawing)?

Are all of the lines connected in common and unused ones should be plugged? Or should each act as a plug? Or are they all attached inside to the loops shown on part #69 (Valve mounting plate)?

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Hold the lines for the EGR. You can remove all lines attached to #71, the T-junction before #63 and the T-junction after #65.

When you say hold do you mean just leave it plugged with no vacuum?

BTW the Central Plug/#71 wound up falling off. I see that it is merely a junction to whatever is hiding inside #69/Valve Mounting Plate.

I removed the line going to the #63 T, the one for the transmission. WOW!!!!! WHAT A DIFFERENCE!!! The transmission is completely different. Upshifts are where they should be and butter smooth (well, for an 80's transmission that is.) It no longer sounds like the entire drivetrain is going to rip itself out of the bottom of the car. The kickdown button is not working and downshift is still delayed so there is still some more troubleshooting to do.

Should the line to #65 (to #71) be plugged also? Or should I tied the #65 & #63 lines together?

Last of all what does #36a, the "Thermo-Vacuum Valve" do? It appears to be a water valve at a quick glance.

I do greatly appreciate the help.

You should seriously consider removing the entire Exhaust Gas Recirculation system from the car, and possibly installing a block-off kit.

__________________
$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Project # 3,248 on he short list of things to do.... .

Well, maybe not that far down the list. It looks like a very simple project. Assuming the block off kit just, well, blocks it off I can machine one fairly easily. Or cast it if it needs to be iron. What are the kits made of?

Here is the CAD sheet.

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Thanks for the drawings.

BTW - did you catch my question about what to do with the other two lines?