[JP Noonan]

K+N makes little round breathers that snap into the vavles covers on domestic cars. It allows the vapor to vent to the outside (polluting the air) but doesn't let dirt back in.

On FI systems there is a very important "flashback valve". It is a t-fitting from the heads then to the air distributor. Inside the flashback valve is a fine wire screen, this keeps a backfire in the intake from igniting the oil vapor in the case. If this were to happen the case can completely blow apart. With that said, my old 32/36 carb had a fitting on the bottom of the air filter housing which was hooked up to the PCV on my 1.8L and the case never blew up.

If you still have the flashback vavle (it is mounted to the bar that controls the cooling flaps, on the fan houseing) I would use it.