I was looking into these Kinugawa wheels. It seems like it's basically just an extended tip design. If you read up on it, the details is that you can have a smaller wheel act like a larger wheel, helping you get more boost and spool quicker. In this application, ideally, the compressor fan tips extend a couple mm more into the housing, allowing it to push a little more air without spooling much slower. I would probably have just ordered these, seeing how cheap they are, but since my X5m is a work truck... I am really trying to sit on my hands to keep from ordering the compressor wheels. You can read about the idea here:
http://www.patentsencyclopedia.com/app/20080229742