stuttering fzs 600

[red98]

evening all....stripped the bike down again today,carbs off and removed the inlet rubbers,there pattern parts and as good as the origanals i dont think i have a problem with these,to make sure i used a smear of instant gasket on the mating surfaces making sure they were clean and re-fitted them,when i first fitted the rubbers i eased the carbs and air filter box back and eased the rubbers out without removing the carbs,its much better to remove the carbs to fit the rubbers,its easier to clean the surfaces and to get to the securing bolts making a much better job,i also removed the petrol tap on the tank to check the gauze filter,no problems there,while i had the tank upsidedown i noticed one of the breather tubes was blocked,looked like graphite grease,i used some degreaser and some mig welding wire to clear the tube and blasted them with my comperssor and a squird of wd40 rinsing with petrol to finish off,all clear now,looked like it had been blocked for some time ,also fitted some new ngk plugs (cr9e) had one slightly loose connection on one of the coils so cleaned and tightened that up and put the bike back together.....the stutter is still there.....flat spot between 5/6000 rpm and a stutter at 8000  :\ :\ :\ 
in the haynes manual it says that a good yamaha dealer can check ignition items off the bike such as coils,cdi and ignition control unit (which i think is the ecu ) has anyone used this service ?
iam going to see a good friend tommrow lunchtime whos just set up his own bike workshop who worked for my local yamaha dealer to see what he thinks,might leave the bike with him to see if he can identify the problem by road testing,your thoughts please folks .....