In this section, “preference” includes: a percentage price preference; and any other provision that favors products or equipment that are mercury free or that contain the least amount of mercury necessary to meet product or equipment performance standards over other products. Beginning October 1, 2003, all State agencies shall give preference to products and equipment that are mercury free or contain the least amount of mercury necessary to meet product or equipment performance standards. This section does not apply to a contract or procurement agreement in effect on October 1, 2001. The Board may adopt regulations to implement this section.