I go with a cleanable in line filter between the crankcase out and the inlet vacuum connection as the crankcase is designed to have a slight negative pressure and on a good/new engine there will not be much combustable gasses leaking by the piston rings so not much draw is needed. Most of us won't drive the car as a race car and this should suffice the requirement of catching the oil contamination entering the inlet manifold and coating the backs of the valves and fir Gdi engines of any make it's a good idea'
Just to clarify for those who have the earlier engine which has indirect injection engines, the fuel is directed at or before the intake valves and therefore a fuel air mix enters the combustion chamber pre mixed. This has the effect of washing the back of the valves keeping them clean so unless you have a serious engine problem you should be fine. Racing and thrashing engines however does cause issues that normal driving however spritely won't cause and racing rules generally require the fitting of closed catch cans which need emptying,
DaveW has recently fitted a cleaning system `as a trial to his Gdi engine so it will be interesting to see haw he fairs with the system. If this works well it may prove a real asset to the Gdi owners cars.
