Another Stutterer

[Soapy]

This sounds most likely to be the carb sliders not doing the right thing to me too. The fact that the bike runs OK at max power if you let it get there gradually indicates that fuel flow, sparks etc are up to the job, but opening the throttle quickly is resulting in the sliders jamming instead of rising at the correct rate.
With the carbs off, apply gentle pressure with your finger from the airbox side of the slider and you will be able to compare how freely they move. Chances are, one or two will be suffering more friction than the others because the PTFE coating has worn away.
When you remove the carbs disconnect the throttle cables at the handlebar first. With them loose at that end they can pull back an extra foot which gives  plenty of free play to get the carbs out... and then disconnecting from the pulley on the carb bank is simple.

Thanks Fazerider. Another thing I should have checked when I had them out. I'm learning the hard way. The bike has only done 3500 miles so is it likely the coating would have worn away already?. But will try pushing the sliders up and see if there is anything obvious.