The S54 engine's six individual throttle bodies have been bored to a larger internal diameter facilitating air-flow to the combustion chamber for further increases in power as well as more immediate throttle response. Core Program: This throttle body set is part of the CORE program we utilize at Dinan so the listed price includes a core exchange fee. This fee will then be refunded to you once your old throttle bodies have been received at Dinan and passed a quality check. This ensures we have a continuous stream of products for rebuilding purposes and the lowest possible price to the consumer. Any cores sent back that are damaged and/or unusable will not be given credit for. Please ensure adequate packaging and packing is being used to protect returning cores.