I know how anal these cars are about air leaks and such, I was just wondering if I put a breather filter on the valve cover outlet would it make the car run bad or will the idle stay the same. I was thinking it would be like taking off the oil cap while the car is running. Thanks

No it wont have and effect on the idle on a 240 or 260 but on the 280s it will . The side effect of a little filter on the valve cover is you will have fumes in the cabin . If this on a carbed Z with the stock air cleaner there is no advantage in not connecting the hose to the the air filter like was done originonally . GAry

It is a 280z, I put a different throttle body on it and dont know what to do about the valve cover outlet now. It went to the throttle body. Thanks for the reply.

run a filter.. you will be fine =)

...or just plumb the breather hose into the intake anywhere ahead of the throttle body.