(a) The manufacturer of the exhaust system must conduct one valid test in accordance with the appropriate test procedure specified in appendix I for each exhaust system selected for testing under this subpart.
(b) No maintenance may be performed on the test exhaust system except as provided by Sec. 205.171-2. In the event an exhaust system is unable to complete the noise emission test, the manufacturer may replace the exhaust system. Any replacement exhaust system must be a production exhaust system of the same category as the exhaust system which it replaced, and it is subject to all the provisions of this subpart. [45 FR 86718, Dec. 31, 1980, as amended at 47 FR 57723, Dec. 28, 1982]