posting this as it may help someone else.
2L DOHC 8v with bike carbs & megajolt
I had a problem when running at redline revs, after a 1/2 mile or so the engine would cough & splutter as if it was running on 2 cylinders, when I slowed down it would be ok
thought it was the coil so changed it, but still the same.
Someone suggested it could be fuel starvation
I have a facet cube pump with the little bullet filter attached which was 5 years old so thought it may be blocked.
I took it off & cut open the filter expecting it to be well clogged but it was still v clean.
I decided to fit a bigger filter to get more fuel through and hey presto problem solved
no more embarrassing cutting out when overtaking etc
photos of old & new filters