I have a 1999 GU TD42 NA
it had the Diesel Gas setup in it when I brought it in Feb this year
from what I can gather from reading all over the place.... its not very helpful to a NA engine, but, much better on a Turbo'd engine
I had mine Dyno'd the other day
while on Diesel only, it was doing 88Kw & 257Nm at the wheels
on Diesel & gas, it was 92Kw & 273Nm at the wheels
not a vast improvement, but enough to let me know, once I get it Turbo'd, it will be a heck of a lot better
cheers