A substitute bill (S.B. 106) to ban the use of most aftermarket exhaust systems has been introduced in the Utah State Legislature by Senator Patricia Jones (pjones@utahsenate.org) and passed by the Senate Transportation Committee. The bill now moves to the floor of the Senate for a vote by all members. Under the substitute bill, all vehicles must be equipped with an exhaust system that is "installed by the original manufacturer of the vehicle and is not modified; or meets specifications equivalent to the muffler installed by the original manufacturer of the vehicle and is not modified."
To contact the legislator in your area see this page from SEMA's Action Network.