Free-flowing exhaust systems may maximize peak horsepower; this is typically accomplished by making the path as straight as possible, using a consistent diameter throughout the system and eliminating obstacles such as catalytic converters and pre-catalytic converters or by replacing the muffler with a less restrictive (and usually louder) one. In a normally-aspirated engine, this often results in a loss of back pressure which may negatively affect low-end torque. (Forced induction engines are not as susceptible to this side effect). Furthermore, eliminating catalytic converters and other emissions control hardware will often render the vehicle illegal for street use in many jurisdictions.

Advantages
• An increase in peak engine power.
• Mileage can be increased.
• Engine sound is more noticeable.
• Factory or OEM replacement part is not available (or is more expensive)
• Aftermarket part is available in stainless steel (but OEM part is not)

Disadvantages
• Most modifications increase the noise level and can interfere with vehicle noise level laws.
• Some aftermarket systems can decrease car ground clearance and can be easily damaged.
• Modifications of the exhaust system can interfere with pollution laws in some countries.
• Loss of torque at low engine speeds on stock engines which are not re-tuned for the flow capability of the new exhaust system. 
 
Please choose between Air Intakes for the "Rover" or "Toyota" Engine.