Sounds like a pretty similar issue I had with my previous '95 945 D24TIC nine years ago. One month after reassembling the whole car it just stopped working at high speed on the motorway, the power was lost and taping the clutch the engine died immediately, in the darkness! Luckily I rolled it out on the side lane, after cranking it about 30 seconds it came back and I was able to drive it on to my girlfriends' place, without another issue, but I drove slower. I drove it a few days later in the city, but somehow it was kinda not running very stable, at higher throttle it decreased the idle rpm, almost dying.
... long story, at all. Later reason (years after I sold the car) one of the new owners in Sweden told me there was big muck in the tank, so it wasn't able at all to get the clean diesel through it and it was pretty jammed.
So the tank and filters needed to be cleaned, then everything was fine again.
Best regards, Bernd
