This is an interesting thread.  I've kicked around the idea of turboing a
WBX for a couple of years.  My main reason for doing it is because it would
be cheap for me to do (labor excepted) and I run my van on propane.  Propane
has an octane rating of about 110, you can use the stock compression ratio
of 9:1 and you don't have to worry about retarding the timing or using water
injection.  I don't think I would want to go above 5 - 6 lbs. of boost.  My
propane system is good for 250 hp so I don't have to worry about
supplemental fueling either.
I haven't done it yet because I have serious reservations about the water
jacket seals and other heat issues.  The same weaknesses the WBX suffers
from already would be multiplied with turbocharging.

Heres a picture of one of the turbo manifolds I make, this one for 1997 -
2000 honda civic
http://www.telusplanet.net/public/gary2a/honda/hondamanifoldahort.htm

Gary Lee
http://www.telusplanet.net/public/gary2a/rack/vanagonrack.htm