t 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, t 1, eff. Sept. 1, 1995.

That seems to be it with respect to exhaust legislation in texas!