Hi gert,
The honest truth is, while it HAS been done, albeit possibly not with the exact same engine, why bother with SDi? If you're going to all the bother of electrifying the throttle and likely all the other electrical systems which go with it, then you may as well go that one step further and go for a turbo. There's plenty in the scrap yards and they aren't expensive.
A TDi'd T25 is a nice thing indeed. I've just been down to Boomtown fair in mine, 780 mile round trip from where I live. Shame the clutch started to go on the way back but I nursed it home
Dave.