Hello,
I seem to remember that there were some old Käfercup
video's around.
One in particular was showing a race during an (also old) DTM raceweekend. It also showed the Z-series bug with the 16v watercooled boxer.
Sadly I don't have that video but I'll ask a friend who has, where he purchased it.
I'll let you know.
Cheers,
Richard