There is NO throttle valve linkage on 80-83 240D. The 80-81 300D was the same. These units use only VACUUM controls.
My previous post most have been misinterpreted. The vacuum modulator is a vacuum diaphram working against a spring (internal to the chamber). The device then moves a piston in the tailhousing. The rod and spring that was part of the original modulator must be removed and installed into the new modulator so that it can move the internal piston.
It sounds to me that this didn't take place and the modulator pressure is stuck in the undepresed condition(similar to high vacuum state).
Your problem started with the modulator replacement, you need to return there to solve the problem IMHO.
BTW there is no aluminum seal ring used on the modulator. Adding a ring can do a similar gross adjustment of the modulator.
BTW again, this transmission is totally different from 82 on transmissions used in any other MB.
Bosch Master, ASE Master, L1
33 years MB technician