Assuming that the Sun Valley folks know their business, it seems that the culprit must be the vacuum control valve. I do not have the service manual for the 240D, but on the 617.95 engine, there is a second orifice in the line between the brake booster tee and the VCV. It is available in five different sizes to allow for variations in supply versus vent volumes. If you have such an orifice, going to a smaller size might be a step in the right direction. It looks like the range of your VCV is adequate, but the vacuum level is too high.
Regarding your question about the switchover valve, the switchover valve usually causes vacuum to be too low, due to leaks in the valve. So it does not sound like the switchover valve is part of your problem.

Perhaps Sun Valley knows what they're talking about but maybe it doesn't apply to my particular 240D??
It does make some sense that there is too much vacuum now because evrything went haywire immediately after I drilled out the T fitting. A new Vac Control Valve is $188, a new vac line from the pump to the booster is $40 something. I think I'll try the $40 something if I can't rig something up tonight that reduces the airflow for experimantation puposes.

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'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)

Do check your vent line to make sure it is not obstructed.

Is that the black line that just goes into the driver's compartment and hangs in midair? I doubt if it is obstructed, but I'll pull the line off at the Vac Control Valve just to make sure.

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'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)

That's the one.

Instead of spending $40 on a line with the orifice, just put in another orifice like the ones mentioned earlier.

That's a great idea - can you buy just the orafice? By orafice I assume you mean the T? or is it something I would install inline after the T?

The main vacuum line looks very rigid - would you have to warm it up to get the T out?

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'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)

Tonight I removed the Vac Control Valve, disassembled, cleaned out thouroughly with brake cleaner, reassembled - still same problem. I had oil in the vac lines due to a shut off valve leak some time ago so I thought a cleaning might do the trick. It was gunky inside but it didn't seem to make a difference. The lowest vacuum I can get it to go down to is 6lbs (the line leading to the trans modulator).

This is really frustrating...I've done so much to this thing since I got it...it was going so well. I just wanted to tweak the 3rd to 4th quick shift/skip and now this

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'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)

You could just install it downstream from the brake booster vacuum line. One option would be to cut a rubber connector and splice it back together with the orifice. On the 617.95 engine, there are five different size orifices to choose from. They are used to balance variations in vacuum supply and vent capacity. (You likely have one already in the line from the booster line. Look for what appears to be a plastic washer between two rubber hoses or connectors.)
We are not talking about replacing the original tee on the brake booster line. The suggestion is to use a seperate orifice instead.

Where do you get the orafices?

I have 2 T's coming off my main line - one goes to the trans vac stuff and the other goes to the HVAC and fuel shutoff valve. One checkvalve between the last T and the brake booster.

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'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)

The orifice should be available from the dealer. They come in five sizes: .7mm, .8mm, 1.0mm, 1.1mm & 2.0mm.
You should have one now; look between rubber connectors on the vacuum line that runs off the booster line.

No, nothing. From the T is a short rubber line then the small hard plastic line plugs in and goes it's way. No orifice. I wonder if the PO removed it for some reason. Does the vacuum diagram show it? My trans is a 722 117. I'll check with the dealer on Monday.
Unfortunately the nearest dealer to me is 2 hours away and they always sound like they have better things to do than look up parts for an old diesel.

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'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)

I don't have the vacuum diagram for the '81 240D. The '82 diagram does show an orifice. But the '81 could be different.
http://www.ultrahot.com/vacuum/fuel_egr_240d_auto.jpg

Just take one of those WD40 red spray pipes cut it about 1/2" long and place it into the T. Its too long to go anywhere and will let you know if restricting the vacuum helps or not.

I don't see anything that contradicts what I wrote in my first reply......If you don't have a Mityvac that's a major handycap since you can't set any reference points.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

I beleive I'm missing the orifice that comes off the T. Thanks to you guys I think that's the problem and here's why.
1. When I was replacing vac lines, connectors etc about a month ago while troubleshooting leaks I wondered why the hard line coming off the T seemed really short and kept wanting to unplug. I had to put in a new section of rubber hose so it didn't have so much force on it.
2. In reading and re-rerading the trans adjust articles one guy said one of the issues he runs across is that someone removes the orifice from the T area and it causes an over vacuum situation which leads to my problems.
3. The diagram Tangofox007 posted shows one where I don't have one.

Now my next problem - I spent 20 minutes on the phone with the dealer's parts guy (they are open Sat mornings) and he couldn't get to thew part - he said their old vacuum drawings are terrible and they run into this when working on old cars.

Anyone know a part number(s) for these orifices or does anyone have an extra one?

I will try Billrei's idea about the WD 40 pipe, but I need to get one of the orifice's or the proper MB part number.

Thanks for your help

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'85 300D - 206K (sold)
'81 240D - 149K (sold)
'03 Jetta TDI - (sold)
'79 300D - (sold)