For California emissions model with catalytic converter. This system does not include a head pipe forward of the catalytic converter, but begins after the converter.
All performance exhaust systems, no matter the manufacturer or type, will be louder than the stock exhaust system. This is an unavoidable consequence of reducing back pressure and therefore increasing performance. This is especially true upon acceleration when exhaust pressures are at their highest. This performance system, with a "Turbo" style muffler ("turbo" refers to the designed flow of the exhaust through the muffler, not to a turbocharged engine), is no exception. This type of muffler, however, was designed to limit the level of sound, especially when the engine is not being pushed. Therefore while it will be significantly louder under heavy acceleration, especially when connected to a header as opposed to the stock exhaust manifold, it should only have a pleasing "low rumble" tone during normal operation.
For coupe models only.
Oval performance mufflers should be positioned at an angle for a proper fit on 70-78 Z cars. Note that for 8/74-78 Z's that still have the original bumper mounts, you will not be able to get quite this ideal of an angle due to interference, but a slight alteration should work fine.