Check engine LIght on at 1600 miles??

[PA-H3]

I recently put a K&N filter in and also one of those tonado things in. My check engine light came on this mourning and when I did the OnStar diagnoses they said it was a fuel system problem. Does that sound right? I know a filter adds air to the air feul mixture but enough to throw a sensor? I was going to take it to the dealer but unsure whether or not to take out the filter and tornado in case that is the kulbrit? I don't want them saying it's not covered under warrenty or something. Any advise???