Frederickk, if i were you, and was debating a VNT, then i would jump on the train and go for it. you wont regret it.
i remember, back when i built my engine, there were only a HANDFUL (maybe a half dozen) older VW diesels using the VNT turbo, and now its a fairly common swap.
the info is out there now, there has been enough research and development (destroyed engines) now to know the limits of things, and such.