L8 and P8 ecu's have exactly the same wiring loom and can be interchanged.
European version of the L8 (green engine cover) also has closed loop lambda control.
If you want things like launch control or ALS, then it's easier with a P8 ecu.
Theoretically the P8 is better, because it has a faster central processor, but in practice I never found any difference in power outputs from a L8 compared to a P8.

And yes, that's an aftermarket chip you have installed.