Hi, I have the same year bike with 4,000 miles. From my experience an aftermarket exhaust can give slight flat spots, which was partially cured (more low down stomp) when the lambda sensor failed (f1 light flashes) and I fitted the smartmoto eliminator, but then fully cured and more responsive when I changed the air filter last year (it was on its original one).
Mine is also on its original plugs, being iruidium they are good for at least 25k repotedly.
Has your air filter ever been changed?
