James,
This is just a "It can be done with a Python". I did the keyless entry and remote start. I will look around and see if I can find the instructions and model number of the one I used. It works great except sometimes if the engine is already warm, it will fail to start.I think there is a minimum starter run time that I could adjust to give it just a little longer time and it would work fine. My car doesn't have the alarm feature so I can't comment on that. I used a switch over valve in series with the ign switch to enable/stop engine.
Thats about all I can remember for now. I did this job about 5 years ago and can't remember what I did yesterday.

But, It will work on a 91 300D 2.5
Paul

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84 500 SEL (307,xxx miles)