i bought a scanner today to check why my check engine light was on, i plugged it in and it gave me this code P0171 which says im running lean, yesterday i had the alternator replaced with one that makes 160amps and also took out the old bosch double platinums and replaced them with AC delco rapid fire. could the new plugs be making me run lean? my car pulls like a bat out of hell tho. should i worry?