Green '01

My 2001 F-150 5.4L had a "System Too Lean" trouble for both banks (according to my hand-held code reader) even though the engine seemed to run fine...smooth acceleration and no rough idle. I tried to clear throuble by cleaning the Mass Air Flow sensor, thought the Volant cold air intake system might be delivering more air than the OBD II could compensate for, questioned Ford service advisor who wanted me to bring it in for computer analyzer ($100), etc. Instead, I bought a can of SeaFoam motor treatment. One tank of gas later and the "Service Engine Soon" light went out. I guess the injectors were dirty. I've only had the truck for a year so I don't know how well the previous owner maintained the truck, but you can bet I'll be using SeaFoam again.