The Td5 injector loom has been a well discussed subject throughout the Land Rover forums for many years. Oil in the ECU plugs on vehicles fitted with the TD5 engine, particularly the Discovery 2 L318, is a very common problem which can cause random running issues.
After changing the TD5 injector loom oil will remain in the wiring so you should periodically clean each end of the loom with electrical cleaner. We recommend daily for a week, then weekly for a month to fully remove the oil. This is also a good opportunity to replace the rocker cover gasket which has normally gone hard and no longer seals. Fitting the injector loom should take no longer than 20 minutes. When re-tightening the rocker cover bolts it is essential they are torqued correctly, evenly and in the right order.