So I took my 90 300TDi on its longest trip this weekend (about 100miles each way) since I got it, mainly dual-carriageway and motorway.
After just under an hour, the revs dropped off to nearly nothing, when going uphill and dropping a gear tio get the revs up gave nothing (5th to 4th).
What I found was that cruising at 55+mph the revs would disappear going up hill (I mean gone not just drop a bit) and I would end up at 35-40mph and not able to get the power down even dropping gears.
Now, cruising at 50mph this doesn't happen at all (it seems), yes I have to give some revs on the hills but its only a small amount.
The question is why is it that if I push that bit too hard on the hills the power disappears completely?
The lift pump was changed a couple of months ago and for the entire of the return 100mile journey (on the same route) this didn't happen at all, did it all at the 50mph mark.