i just got this question.....
the "engine check" shouldnt be on even if you installed the headeR, are you sure you installed the Oxigen sensor, and if you did did you put threat seal, so the vibrations wont knock it off???
the ecu controls your engine, it controls from fuel injectors, to VTEC if you drive honda/acura you gonna have sensors every here in the engine/exaust, on my accord theres one just about everywhere header, cat, intake manifold, oil pa, well you name it and theres probably one
