We marked the underside of the car at the rear edge of the catalytic converter flange. This allowed us to be sure the new system was in the proper fore-and-aft position to ensure proper alignment and positioning. Here, barely visible, is the hose clamp that holds the A.I.R. tube in place on the passenger side as seen from below. We're not sure when this clamp might have been installed when the car was built, but there's surely no way to get any kind of screwdriver on it or even a 1/4-inch drive socket, so we used a small box wrench to loosen it.