I have WI just after the throttle body and just after my M90 supercharger on my car and it works very well. I've got a small yellow jet before the supercharger and a bigger blue jet afterwards. My car is a Ford Sierra, similar to the american XR4Ti but with a V6 engine and 4 wheel drive, with a bored out 2.9l engine (now 3.7l). Take a look at
http://www.xr4register.com/profiledavidward.php and click on the supercharger pictures at the bottom of the page.
Dave