98 F150 4.2 V6. Here i am again code po171 system too lean [bank 1 ] came up. I cant find any vacume leaks i changed the pcv and the rubber elbow under the plenum is good . I switched the the sensors in the exhast and the problem stayed on bank one only thing i can figure is the MAF sensor is bad or i missed i vacume leak . Any help would be greatly appeciated.