I ain't familiar with a transbrake system but can you disable it & see if things go back to normal. As you know it is definitely having an immediate effect on the ign. EDIT you said turning on the trans br stopped the ign. is that as in made it die or is it making it act up with the same symptoms happening when going down the track? & if so (especially the 2nd one) that would easily point to the TB as the culprit