The manufacturer must include the following statement pursuant to § 205.173-4 with each product of that category the manufacturer distributes into commerce:
Tampering Prohibition
Federal law prohibits any modification to this exhaust system which causes the motorcycle to exceed the Federal noise standard. Use of the motorcycle with such a modified exhaust system is also prohibited.
Acts likely to constitute tampering include removal or puncturing the muffler, baffles, header pipes, or any other component which conducts exhaust gases.
40 C.F.R. §205.173-2