One other thing to check, on the Z8s they place a prefilter bag over the end of the air intake tube to limit the amount of larger materials entry to the box. This does get filled and causes increased vacuum on the box which also pulls harder on the crankcase tube..pulling more oil and vapor to the box.
I know the 500s have another issue with baffling but I guess I didn't know the 550s had the same issue.