Bully Dog Technologies' Rapid Flow Exhaust systems are great for reducing exhaust temperatures and increasing horsepower and economy. The rapid flow exhaust are 4" - 16 gauge aluminized steel systems that boast the lowest degree angles on bends in the industry. This free flowing, low backpressure system gives you lower exhaust temperatures, lower interior resonance, more horsepower and torque. This allow the turbo to provide air more freely, reducing exhaust temperatures by as much as 200 degrees. This Rapid Flow designed for the LLY is a cat-back system.