Update, after stripping the carb theres no signs of a blockage, gave it a good clean and checked everythin over, all seems ok, besides the main o ring\seal been a twat to put back together.

After lots of little adjustments on the mixture screw (stupidly possitioned), its almost running right again, instead of the rev chugs happening round 5k its now hitting 8 and 9k before it happens, so another few small turns and then back of the idle mixture screw and it should be spot on again, then ill pull out the airbox and make sure its not pulling air in from any holes etc.

Not sure whats gone on tho, the dealer only swaped petrol tanks, so i cant see them having messed the mixture up, the pipe going from the fuel tap to the carb was also replaced for a bigger pipe, but that would'nt cause it would it?