Hi Matt,
The white and yellow wires:
These are the two sensor wires from the two integrated potentiometers inside the throttlepedalpoteniometer.
If the readings of the two sensorwires differ too much, the ecu will bring the car in limp mode for "safety reasons".
I had that once, overtaking a lorry, driving between two other cars at 130 km/h!!!
VERY DANGEROUS action from that ecu in those circumstances!
If you link the two sensorwires to eachother, there will never be different inputs to the ecu anymore bringing the ecu to go in limpmode.
A Maserati specialist told me this "invention of mine" was a factory mod later on, because they too agreed this "safety thing" backfired sometimes in a very bad way!
Hope i was able to explain, otherwise please comment.
Luuk.