The ECU is an interesting suspect. The symptoms certainly point in that direction, especially the commonality in the idle jump speed that our bikes share.
So, what could go wrong in the ECU?
- the bike couldn't have come from the factory like this.
- the ECU code is unlikely to age
- digital logic is also unlikely the age
- analog stuff could certainly age, and it's worth cracking the box for a look
I'm of the opinion that the bike may have been tuned right on the hairy edge and after some wear in the air/fuel system it triggers this problem.
Maybe being able to tune the timing in the ECU could actually "fix" the problem.
Perhaps I'm only reiterating what Ben said, but I'm certainly curious to find the root cause.