This won't sound very helpful but if you've swapped rev3 ecu for rev 3 and still have a problem either there's a genuine fault still there or you have a wiring problem.

If now you're not getting fault codes then probably wiring is most likely assuming that the ecu's haven't been damaged.

You could try checking continuity through wheel sensors and testing everything else for short to earth.

Might be an idea to take the instrument panel out and have a look at how the speed limiter has been fitted to check it isn't affecting any tracks on the pcb.
