running probs 900ss

Hi again got the ss running ok few weeks ago hi comp pistons twin plug heads etc had a slight stumble about 5-5500 rpm this has gradualy got worse wont often pull through this but when it does it hesitates almost like it is waiting for the slides to lift then another delay before fuel comes through other times it will just sit there just sort of spluttering/missing have got new plgs new fuel filter timing checked float hieght ok all jets clear dont know what to try next Steve

STEVE being slowly driven mad by my duc but loving it ------mostly