Folks,
Since my first posting on this thread, I have done several things in an attempt to address the shifting problems of my 1987 300 SDL OM603 engine equipped vehicle. But I still am having a problem. Here's the history:

1. Shifting very early and softly. Rapid shifting back and forth between 3rd and 4th at speed.
2. Checked bowden cable adjustments, okay.
3. Checked vacuum from the amplifier to the modulator, found leak in modulator.
4. Replaced modulator and set pressure as described in on-line doc's.
5. Still have problem. If disconnect vacuum from modulator, shifts fine, just too early. Re-connect, bad between 3rd and 4th again.
6. Replaced all old hoses, cleaned ports to intake manifold, etc.
7. Vacuum control valve bleed port clogged. Replaced this valve.
8. For grins, replaced both vacuum switchover valves.
9. With Mity-Vac, I'm getting good vacuum reading when connected to vacuum source line at amplifier. But when connect Mity-Vac to source line with a T-connection to amplifier, I get no vacuum. I plugged off line to modulator on the transmission, and still get no vacuum, just free flow of air when suck on the vacuum source connection on top of the amplifier and the two bottom hoses are connected normally.

Question: does this mean my vacuum amplifier is leaking / broken internally? Or is something connected to the bottom lines leaking? I wish I knew how the vacuum amplifier is constructed internally.

I'd appreciate any help of advice before purchasing a new vacuum amplifier.

John