I dunno about the wire Tom doesn't like (I haven't tried it - but his word's good by me), I have however tried both a resistor cap and plug with success (NOT at the same time tho - that'll cause probs fosho).
I'm not sure how much success you'll have with a
wireless speedo, but it stopped my wired one from hearing voices and speaking in tongues - I suppose a combo of Tom's suggestions and a plug might do the trick...
BTW, plug is the same numbers - just with an "R" added, the caps work a lil better but look funny *shrug* Whichever you pick of the "resistance" options - use only one else yer spark may suffer