(5) Muffler and Exhaust System. Accelerate motor to test for prevention of unnecessary noise and emission of any unreasonable amount of smoke. The exhaust system, exhaust manifold(s), exhaust pipe(s), muffler(s), and tailpipe(s), if designed to be so equipped, shall be tight and free of leaks. System components shall be securely fastened with fasteners in place and undamaged. All motor vehicle exhaust systems shall discharge the exhaust beyond operator, passenger, and/or trunk compartment. Unnecessary noise is herein defined as any noise which is louder than that emitted by the vehicle when equipped with the original manufacturer's equipment. A gas or diesel vehicle will be rejected if, at normal operating temperature, at any constant speed over 15 MPH, (approximately 1,000 to 1,200 RPM's) visible black or blue exhaust emissions are evident.