its a common problem, mainly with earlier models, change the injector loom, its not expensive, if the oil has worked its way to the ecu you can clean it out with brake cleaner, it wont damage the ecu as its sealed so the oil wont get inside. also clean the plug on the engine loom to injector loom
I have changed engine looms in the past where they have been soaked in oil but now i just clean them and they seem to be fine