If dealer installed a larger main
jet, that has no bearing while decelerating, at that point you are on the pilot
ckt, all he did was to make you richer on the top end. You are better off not changing air jets, they also affect the vacuum pressure to draw fuel up thru the carb
If using modified stock pipes or after market pipes, the AIS
needs to be removed.
You don't say if the K&N filter is in the stock housing or if it's a open filter. If it's an open filter then you need to do a full jetting, if in stock air box, could be as simple as a pilot screw adjustment.