The throttle position sensor sends a signal to the computer for the EGR.

The difference in the '85 shifting is the different torque converter and the "blue flying saucer" which takes boost into account when sending a vacuum signal to the transmission. '85 was supposed to be the best shifting year.

http://www.peachparts.com/Wikka/TransVacTune

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

UPDATE:

The guy lied about the wagon except for one thing. It had no rust or very little. The rest of the car was trashed, had dry-rot on the tires and the belts had rubber flapping when the engine was running. I told him there was no way I could drive the car back to Miami!!! The driver's seat looked like a thousand pounder sat it in every day and they patched the scratches and dings with paint that didn't match the faded original. The best of all? Never seen so much Super Glue on a car!!! His son had run it through a car wash and ripped the antenna off. They Super Glued it with a big wad of glue. One of the taillights was glued. He kept going on and on about the little tools it had with it and how collectible they are. And before we even turned it on, fluid was leaking out towards the rear. Don't know. He probably started it before I got there to make sure it would start. We even went for a test drive. I had flown up there from Miami and thought maybe something would wow me. The engine was making all kinds of noise (not usual - had one before and know what they should sound like) and pick-up was extremely slow. I ran as fast as I could!!!

The guy was nice but I hate it when people lie about their cars. Just tell it like it is!!! He made it sound like it was so pristine. It was so baked from the Florida sun that it could have been a potato chip, extra crispy!!!

The plane ride was fun and I got to go to Costco. Not even a mechanic could fix this one. Major project!!!

I appreciate my pristine 560SEC with 161,000. Now that car has been taken care of. It just breaks my heart when I see such an incredible car wasted like that!

So I am going to take a deep breath and keep shopping for "that diesel."