Valve cover breather on non boosted cars

[Joshua]

Just a little word of advice when you remove forced induction from your vehicle also remove the valve cover breather filter. our cars run on a closed pcv system that requires the valve to be sealed. I kept getting P0171 and P0174 which are bank 2 and bank 1 lean conditions. I replaced my MAF sensor and checked for vacum leaks, couldn't find any until i was thinking about the breather filter and placed a plastic bag over the filter and noticed the vacum on it. I also have a scanner and noticed the fuel trims were extremely lean with the bag on the filter 19 across the board. with the bag on they dropped to zero and below. Needless to say went and bought a new oil filler cap and no problems. at anyrate now i've got an extra MAF and zzp breather layin around.