Ok, The surging I am experiencing is at slow speed the bike feels it has a flat spot and a little hesitant but as soon as you blip the throttle a touch its fine, another example would be kind of fuel starvation.
But all in all I take no notice of it now I have done a couple of hundred miles on the bike.
I have looked at the numbers on the ECU as requested and they read 5VK-8591A-11. Hope this helps and look forward to your expert findings.
The bike is a 59 model xtx with 2000 on the clock.