When i was driving this morning, in tip mode, i noticed when i shift from 1st to 2nd the rpms will dip slightly. like once it has totally shifted it will almost lose power for a second. i thought maybe fuel filter, which has 140k on it, so i changed that today. and i also changed the spark plugs which where also original to the car. i replaced them with oem nkg plugs. all of this did nothing. any ideas?