Getting back to your original problem of white smoke, it may be head gasket.
A Defender 300tdi I bought a few years ago had exactly the same symptoms as yours - Lots of white smoke when warmed up, ok when cold, pressurising the crankcase.
Didn't notice any power loss though.
Problem was the head gasket blown from no.1 cyl into a pushrod hole. Loss of compression on no.1 cyl = unburnt fuel out the exhaust.
The leak must have been opening up with temp. increase.
Hope you get your fuel problem sorted, sounds like you do have an injection pump problem, hopefully that's all it is.
Terry
80 109" 2.6 P ex Army GS, saved from the scrappie.
95 300tdi 130 Single cab tray.
2010 Guzzi 750
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