well...as an update, i took the cylinder head off at the weekend, onE valve was indeed heavily pitted and there was evidence of the valve not seating correctly (this was on the cylinder with low compression). i replaced that valve and re-ground all the others

took the car out, and it was exactly the same...still a mis-fire

interestingly though i disconnected the throttle position sensor and the mis-fire almost went...it will rev right upto the limiter, with a slight hint of mis-fire around the 5500 mark...so it looks like im heading in the right direction to finding the fault at last, although the KAM didnt register a fault with the TPS??? so maybe its not that? any ideas on checking the TPS?