It really sounds like you have air in the fuel which is causing the stall from a cold start. Is the clear return line from IP to filter housing brown with age? I think a new line is available. I'd strongly suggest you buy a new one so you can see what's going on and chase down the leak. It's a pain to find air leaks.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked