Surging at 3-4k RPM

[Flyingwombat]

So went on Reddit and was given a list:

- Relays
- Ignition coils
- Crank position sensor

[London_Phil]

Honestly cant se any of those...well maybe fuel pressure, but the cps generally will cause it to cut out, and coils will run rough rather than surge imho.

[the slow heart]

We have problems ... and this is not going to change,
then lets acknowledge the progress, to keep the faith -
well done compression testing, no mechanically caused leaks at number two.

ECU and coils are quite tricky to diagnose in home environment,
but you could swap items guessing. Can you get other ECU module, proven as operational?
Same for the ignition coils, you need friend with our bike model.
Would join the fighting alliance, but I am damn too eastward, mate 

[the slow heart]

Honestly cant se any of those...well maybe fuel pressure, but the cps generally will cause it to cut out, and coils will run rough rather than surge imho.

You are probably right, but since no better idea is coming, we have to just check the boxes remaining.
Vacuum leak may interfere with the pressure sensor/ IACV to cause surging,
but backfire has to be ignition/ timing related.