1990 300D 2.5 Turbo Transmission adjustment

I have a 1990 300D 2.5 Turbo with a problem.
I was having a power problem with my 300D, and discovered a torn vacuum line on the turbo actuator! Fixed it and the power seems to be good.
However, I'm noticing the trans is shifting through the gears to 4th before I hit 20 miles an hour, and even the firmest foot to the floor will not initiate a down shift.
I can do it manually from the console, but curious if anyone can point me to the likely component, or adjustment. Could it be yet another vacuum line. I've looked but have not found one amiss.
The machine has 160K miles on it, and is running great, save this little quirk.
Tim
P.S. I won't go into detail, but my confidence in Mercedes dealer mechanics is at an all time low. A lot of Bozo working those things in my experience.
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Re-check ALL of the vaccum lines and fittings. Today while tying to solve an unrelated problem, I replaced a short section of line that looked like it was probably okay but marginal. As a result, all of a sudden my 300SDL is shifting much smoother and not clunking into gear as it sometimes would!
Good luck!
None wrote:

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I've done a pretty thorough check of the system, and although I can't be positive, I can't seem to find a leak. I'll keep looking. Is there any components, tranny-wise, that I should suspect? Any adjustments I can make?
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