Pulled my codes again for the second time tonight after getting the CEL. This time I only had one (last time two)..P0171: (System to lean Bank 1). Im not a mechanic, so this is a bit above my level of knowledge. Gimme electronics and I dont have a problem, but internal engine is not my thing.

Any info would be great, I dont want to just clear it again and forget it this time.

Only mods..Injen cai, Stillen cb. This happened prior to the Stillen and several months after the Injen.