84 300SD stalls from cold start when put into reverse

[JiveTurkey]

Heya Diesel Peaches,
I've been bringing the '84 300SD up to steam slowly over the last few weeks. In the last two days a new issue has reared it's head. From a cold start the engine idles more roughly than it used to and stalls when put into reverse. The idle is a little lower (around 500) than it was when I bought the car (around 750). When the engine is warm, or even halfway warm it operates normally at all engine speeds. I havent done a compression test and there's not a lot of blowby.

I've been doing little stuff to the car so far
-new glow plugs (bosch)
-new glow plug relay
-voltage regulator to the alternator
-tightened AC compressor and alternator belts

I've been running good diesel with treatments every fill up since I got the car.

Any ideas?