According to the information in fig 1 the SRIS tube from the front side should go from the left cylinder inlet ( see the label C in fig.2) to the center cylinder SRIS outlet port. The SRIS type 2 system. Center to Right and Right to Left, all according to fig.6-13 from the manual

Fig.1

Fig.2

From left cylinder inlet

Fig.3

To the Center cylinder SRIS check valve outlet.

Fig.4

Fig.4 shows the two remaining tubes. From Right to Left (red arrow) and Center to Right (yellow arrow ) .

The check valves are all cleaned and the function is back to normal. The filter connected to the plastic part at the end is missing. I assume it is not possible to get hold of new ones ? I’m told its not a critical issue. If the valve get clogged no harm will be done to the engine.