Hi,

I am pretty sure that the fule filter is ment to be a lifetime filter, so i doubt that is the problem... is your check engine light on? might be a O2 sensor. did you change wires when you changed plugs, i doubt that would be the problem... just trying to rule some things out.. Also i would try some fule injector cleaner.. might help..

Hope i helped some
Better Bob
PS sorry bout tha spellin, n' stuff