Which of the following is NOT a valid reason for failing an exhaust system?

A valid reason for failing an exhaust system would involve factors that compromise safety, performance, or emissions standards. In this context, securely fastened components is a sign of good installation and maintenance, which actually aligns with safety standards. A properly secured exhaust system is essential to prevent leaks and ensure the system functions correctly.

The other options reflect conditions that would warrant a failure. The presence of exhaust cut-outs can indicate an attempt to modify the vehicle's emissions system, which might not comply with regulations regarding emissions testing. Louder noise than factory specifications suggests the vehicle could be operating outside of regulatory noise limits, which is often used as a basis for failing an inspection. Finally, leaking exhaust is a clear safety hazard as it can allow harmful gases, including carbon monoxide, to enter the vehicle cabin or the environment.

By understanding that securely fastened components indicate proper installation, one can see why this would not be a valid reason for failing an exhaust system.