Not sure which 2006 BMW Z4 Air Filters are right for you? We have over 69 customer reviews, with an average rating of 4.5, to help you find exactly what you're looking for. Warren B from Estero, FL said, "AFTER INSTALLING THE K/N FILTER IN MY CORVETTE MY GAS MILAGE HAS IMPROVED AND MY POWER TO THE REAR WHEELS HAS IMPROVED, THERE HAS BEEN NO CHANGE IN THE IDLE OR HOW MY ENGINE IS RUNNING, SMOOTH CONTRARY TO WHAT SOME HAVE SAID ABOUT THE FILTER. A WISE INVESTIMATE. WARREN BLOCK"