OK, now we're getting somewhere... maybe.
The car is a 3.0 V6 12valve; never sold new in the UK. I have only come across two, one was a (bad) conversion to RHD and the other original LHD.
The fuel injection relays are among those on the bulkhead at the back of the engine. Originally they would have been metal-cased Bosch relays, one possibly having a red diagonal stripe on the top. However, bear in mind someone has probably already been there, and they may have been swapped around already. Also check any fuses in this area.
Another thing: does the car have any after-market alarm/immobiliser system fitted (or any evidence of) ?
Before going any further I think it would probably be wise to make sure that the injection warning LED has not been "disabled" by some unscrupulous person in the past.
Being a conversion also brings it's own problems, as there are likely to have been a number of modifications made to the wiring loom, as well as re-routed cables etc. This means increased likelyhood of bad connections and chafed wires. On RHD cars the ecu is in the passengers' footwell, with the fusebox and code box in the drivers' footwell, as they are now on your car. This means that the entire fusebox/loom and code box have been relocated, so be particularly suspicious of any non-standard looking connectors or wires.
RHD cars have a connector in the loom between the code box and ECU which is found under the heater unit, and sometimes causes problems due to coolant ingress from a leaking heater valve. Now this connector will have been moved (assuming it's present at all on LHD cars), but you should be able to find it by following the wires from either the code box or ECU.