Ducati Monster S4R Owner's Manual page 151

Tampering warning
Tampering with Noise Control System Prohibited. Federal
Law prohibits the following acts or causing thereof:
(1) the removal or rendering inoperative by any person,
other than for purposes of maintenance, repair, or
replacement, of any device or element of design
incorporated into any new vehicle for the purpose of
noise control prior to its sale or delivery to the ultimate
purchaser or while it is in use; or
(2) the use of the vehicle after such device or element of
E
design has been removed or rendered inoperative by any
person.
Among those acts presumed to constitute tampering
are the acts listed below:
(1) Removal of, or puncturing the muffler, baffles, header
pipes or any other component which conducts exhaust
gases.
(2) Removal or puncturing of any part of the intake
system.
(3) Lack of proper maintenance.
(4) Replacing any moving part of the vehicle, or parts of
the exhaust or intake system, with parts other than those
specified by the manufacturer.
This product should be checked for repair or replacement
if the motorcycle noise has increased significantly
through use. Otherwise, the owner may become subject
to penalties under state and local ordinances.
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Problems that may affect motorcycle emissions
If you are aware of any of the following symptoms, have
the vehicle inspected and repaired by your local Ducati
dealer.
Symptoms:
Hard starting or stalling after starting.
Rough idle.
Misfiring or backfiring during acceleration.
After-burning (backfiring).
Poor performance (driveability) and poor economy.