Sec. 547.604. MUFFLER REQUIRED. (a) A motor vehicle shall be equipped with a muffler in good working condition that continually operates to prevent excessive or unusual noise. (b) A person may not use a muffler cutout, bypass, or similar device on a motor vehicle. Acts 1995, 74th Leg., ch. 165, Sec. 1, eff. Sept. 1, 1995.