Yes I know about resistor plugs, although this is mostly used to damper the ectromagnetic field. Besides the noise may come from the new EV14 as well.
The topic is more about the PS/2 cable which may work as an antenna, the plugoff message which is not a simple alarm to be acknowledged but which stalls VT and the need of a good GRD.
I have scoped the spikes at the PS2 cable, quite impressive, the GRD can jump up to 3V. In fact Iwould be surprised if the source is only electromagnetic.
Anyway I would supress the PS2 (anyhow said as "not recommended"), make the wiki wheelspeed circuit with zener and lowpass filter and go for a "stronger" GRD earth... Last note, the Genboard V6 seems to be more sensible than the V8 ...