ok maybe i dont have a problem after all. today took it out on country lanes with little traffic and tried revving it in neutral, no issue with that, then set off and gave it some stick in first and second, again went to redline easily. tried this a few times and was fine so got on a better road and rode it like i stole it for a couple of miles. oops 80mph! I still feel a slight hesitation around 5k but revs fine. I think i was expecting too much low down power and forgot they need revs and plenty of them. thanks for advice guys and will report back with any developments