[ischmitz]

Another possibility is the output stage for the fuel injectors is damaged. It could mean that the ECU can not reduce the fuel pulse length at the lower end and "leaks" too much fuel into the engine during idle.

The 3.2 Carrera injector stage is somewhat special. It uses a peak&hold driver to control the current to the low-impedance injectors by pulse width modulation. It also has a flyback supression stage to dampen the fuel injector response and absorb the voltage spike that occurs when switching the current to the injectors off. If that stage isn't working the injectors are not switching off fast enough but "ring" for a fraction of a millisecond.

You need an oscilloscope to compare the injector current with a known good ECU to check if that is what is going on.

Ingo