I have looked into this at great depth.
The Nissan VVT has 2 cam positions, the HKS is variable.
Yes, if you have enough time you can modify your camshaft to have oil feeds to activate the pulley on the end.
Sensors are not really an issue but driving the setup must be a bit of a faf on the outset.
Delph worked with GM to design an electonic VVT pulley, oil free. Though would be bloody great as you can now have VVT on both cams.
However, I don't know what came of it..
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