Ok got an 05 gs500f. Just replaced the air filter with a stock paper filter. As far as I know its stock carb jets. And has stock exhaust. So after I changed it I noticed a very defined hesitation in fourth fifth and sixth gear when hitting the throttle hard to accelerate. Wont do it if you just ease up on the throttle it gains speed nicely then. But if I try to hit it hard it drops rpm slightly and then slowly gains speed. Im totally lost and any suggestions or possible causes that could be advised on would be well appreciated.