The EFI ECU controls the fuelling based on the various sensors, testing the workings within the ECU isn't a diy function, but as the EFI coolent/engine temperature sensor is the most common one to fail and will cause over-fueling when engine is up to temperature, this can be tested, resistance data on that and sensors can be found on the LRV8 engine sites (such as mentioned in the post above) and Forums... or replace it.
Just to add: if over-fuelling on a cold start indicated by lots of black smoke then the ECU is/ or maybe faulty, as I found out in my 3.5 days, main Dealers didn't have a replacement so I took it to Lucas and they bench tested and repaired it while I waited, those where the days when Lucas was everywhere but still cost £100 for the repair.
