You've been led in the wrong direction. The K03 from a 1.8T was
designed for a 1.8T and not a 2.8L VR6. The turbo will be too small
for a VR6 application. Even if it did work, the K03 would not be any
more reliable than any other aftermarket turbo because the VR6 wasn't
designed as a turbo motor. As such, you will still have to add all
the necessary plumbing, exhaust manifold, intercooler, etc. Also, you
don't really need valve work for your "basic" low-boost turbo setup.
Check out www.8vturbo.com, www.matrixmotorsports.com, and
www.hpamotorsports.com for turbo information. Keep in mind
that you'll be spending at least $4500 for the turbo parts, not
including installation. Plus, I'd recommend other upgrades as well,
if you haven't already done so. Suspension, brakes, wheels/tires,
lower dogbone mount (for a Mk4), etc. You cannot just slap a turbo
on an otherwise stock VR6 and call it a day. Gotta do lots of
research....but this is a start.