Does anyone have any feelings on where the most common place is for blockages? The "y" shaped pipe at the rear seems to be a favourite and it's difficult to imagine how that could be improved really. Granted the plastic bit on top of the plenum is difficult to clean out and largely cosmetic but if crud is going to get into the system it will anyway.

Regular oil changes and breather cleaning is probably the best answer. Without wanting to start an oil thread some oils are probably more prone to foaming and forming mayo than others, but I've not done any testing.

Kevin