FJ1200BristolRuss

Hoping someone can help! When I bought it I took it for a few short rides - no issues. One day it really didnt want to run and was only runing on a few cylinders. I thought it was dirt in the carbs so cleaned them out - pilot jets werent great so took the opportunity to replace. No change. It seemed like it could be ignition issues so i replaced the coils - no change - I then found that one of the plugs was faulty, so replaced all and it then idled well but would bog down/had no power. To me it seems like its got to be the carbs, I just cant tell what difference it is making when i pull it apart and rebuild it. Everytime it purrs after the build and im grinning like an idiot for about 3 miles before the issues start.. The issues are that it will idle pretty happily but opening the throttle past 3k will result in the engine 'hunting' and dying out. Adding choke just makes things worse. The bike is factory engine wise other than a free flow exhaust. So far I have: Changed coils, spark plugs changed the fuel new fuel filter replaced carb gaskets, float needles, idle jets, main jets, new battery Diagnositics Tried running with petrol cap open and shut (no difference) Checked pump operation Checked float levels checked diaphram for damage reset mixture setting to factory (+plus 1 turn to take into account the exhaust) Inspected fuel bowls (clean) the most recent item was the float needles - i though perhaps it was getting over fuelled. After I rebuilt it all - again, runs perfectly for 3 miles and then i have the issues. any ideas?