The BMW S85 engine is built with ten throttles bodies, one for each cylinder. Dinan takes each one of these stock throttle bodies and carefully bores them to a larger internal diameter, enabling each cylinder to breathe more efficiently. This increased efficiency translates into increased power output and improved throttle response. Stage 2 Engine Software is highly recommended for optimum performance and drivability. 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.