My Z with the 54mm idles at 900-950 RPM. The one I tested flowed 1.1 CFM more than stock. Stock was a little cruddy so that may have been the difference. The IAC can compensate for a small leak anyway. Leaking at the throttle shaft however is another story. Thatcan cause lean conditions at idle/cruise and rich conditions underboost. Air leaking or escaping post MAF is not good.