my moneys on a ignition problem, or maybe even EGR. if EGR... just block it and deal with the light. or buy a dash hawk and keep it cleard.

 

I dunno here, if there wasnt any real performance change Id say possibly the EVAP system, my light came on last October and I didnt get around to fixing it until a month ago LOL. If it is major, fix it, but if its evap circuit malfunction, dont sweat, the problem cant get worse than it already is.