Sly Bob is absolutely correct. The J pipes are used to eliminate certain frequencies of drone depending on their length and diameter. They do not sacrifice tone or performance, as only sound waves enter the J pipes. They are actually cool to the touch, if you were to feel them after driving. They adjust like a trombone, and are capped off at the end. As you slide the J pipe in or out, you are changing the frequency of drone that is cancelled out. The larger the motor, the smaller the J pipe. A 4 cylinder car requires a huge J pipe, which is why we do not use them on the Kappa's. First, they are not needed because of our muffler design, and second, they would not fit under the car. The J pipes also work well to hide the change in sound on the V8 cars that have the displacement on demand feature (the car goes into 4 cylinder mode when being driven for fuel economy). On many of those cars, the exhaust note becomes harsh, and the J pipes help to lessen that and remove any interior drone from the change.
