Hi Steve,
Functionally there will be no discernible difference. However, having said that, the air filter is a little further clear of the firewall, so it may be possible to run a slightly larger filter. Some of the folks running high boost have encountered flow limitations with the old filter.
The supercharger to cylinder head manifold is a modification of the old tooling. It extends a little farther forward, and the blower itself has moved slightly. There is no longer a bypass block on the back of the charger. With the internally bypassed blower (same as used in our Spridget kit), the vacuum pot for the bypass is now located on top. The carb is now mounted directly to the blower using only a thin adapter plate.
A casual observer may not notice any difference between the old and new kits, but unfortunately, only the pulleys are compatible. Pretty much everything else is "similar but different." We don't expect any measurable difference in performance.
One item of personal interest is the bypass block. It has to be on top of the blower because the exhaust manifold would melt the plastic vacuum pot. I ran my Midget for a while without the bypass and never really noticed any difference in mileage. With a little testing, for visual reasons some folks may choose to remove it. We've never really done any extended mileage tests to determine the efficacy of the bypass.
Cheers.
Robert Goldman
VP Business Development
Moss Motors, Ltd.
E-mail: rgoldman@mossmotors.com