^ A long extension, and a swivel socket will easily solve that problem. To replace the sensor use a strip of electrical tape to fasten the sensor to a coat hanger. Feed it in through the front of the intake manifold near the throttle plate. Pack the tip of the socket with dielectric grease to hold the bolt in while you maneuver the extension into place. It takes a little finesse, but isn't terribly difficult to do. I tried using a super long needle nose pliers, but clearances under the runners were way to tight to actually make it useful. (That's with emissions and pcv removed)