Speedo relation to ECU (Help)

[Dr-Rotor]

Dose anyone know if the speedo is related to the ECU? Our other FD had a reverse light issue that we were trying to sort out. My mechanic was checking to see if there was power to the plugs on the gearbox, while he was doing this he sparked one of the plugs with some gaget he use for checking power.
 
We did not find the falt for the reverse lights but put the car on the dyno for a little tuning. I saw that the speedo was no longer working and the power graphes had a sign wave pattern on the top end. The fuel economy has halfed & the car has very light stutters in smooth driving at 3k in 3rd.
 
So this tells me the car needs the speedo reading to function properly...Could that sparking of the plug have stuffed some sensor and put the car in limp mode? It has a PFC ECU. All the fuses are fine so its not that & we have fixed the reverse light problem, it was a stuffed pin in one of the plugs under the dash.
 
Any ideas?

[Timmy]

I don\'t think it is, can\'t 100% but i used to have a apexi rsm when i removed it i didn\'t get the bullet connector re connected properly. The ecu was showing 0kph but the speedo was still working. Unless the signal is split before it gets to the ecu.

[shaunwil]

The signal goes into the speedo and then out to the ECU. I ran with a convertor for a while with the signal off to the ecu removed. Seemed ok and only reconnected it when I refit the PFC. Easy way of possibly removing the 118kmph speed limit.

Shaun

[Dr-Rotor]

Thanks. Will be tuneing on the way to work tomorrow to see if i can sort out this fuel problem.