OK GUPPY, sorry, fair question now
That looks like:
a) A helluva lot of kit for the price
b)
On the surface well specified and made stuff
c) Not a specific engineered solution for vanagons/T25 (even the engine type isn't mentioned AFAICS)
d) A generic set of kit, which has been no doubt advertised for countless types of vehicles, that is, Vanagon has just been thrown into the title to attract seraches on vanagon, little more
e) Designed to 'possibly' produce 'acceptable' reslts on variety of engines (i.e. the cut of the turbos jib would be a compromise, but maybe offers good adpatability to gas flows, a wide range of boost settings etc)
f) The intercooler pipework would need additional pipe and work for an upfront installation and would be out of the question for an air-to-air intercooler anyway, so would have to be at the back (somewhere v.difficult to position ina T25)
g) the manifold as they say, requires adaption and welding as would the exhaust to accomodate the wastegate flow (too loud to leave it open)
h) kit mainnly intended for fast/track vehicles
i) Fully installed and well setup and set to 5~7 psi, you should get some decent performance from it.
j)You might also get a shedload of problems, in running, detonation, economy, lag (though might be OK, that's where the specific engineering solution for a specific engine scores, as well as safety)
k) It is normal to run a lower compression ratio on turbo engines, hence the low boosts you could prob. get away with, but one incidenece of HSD (High Speed Detonation)and probably bye bye engine
I suppose I could go on, but unfortunately not a turbo installation engineer, nor have a crystal ball...
What you would need I suggest is to find someone else (in US?) who has applied this kit to vanagon 1.9 and done a lot of the troubleshooting that it would no doubt require. In short, allow a lot of time, more money, and have a spare (ideally brand new) engine sitting on blocks just in case.
PS. They didn't get 1.9 in US petrol vanagons IIRC, just 2.1 MVs (more suitable than 2.1 DJ due to lower compression)