although i dont normally agree with snop, im with him on this one... i think those 35's are too much for s 350. i dont remember if he said what pipes he is using either... but like always if your intake, porting, and pipes are not working together your loosing power. just becasue your bike "runs good" with them dosent mean your getting your maximum power delivery from the motor across the powerband.
i say ditch them and get some 30's unless you ever plan to go to a bigger motor then keep them.