Parts & Accessories Spare parts The exhaust was used for 3 months without any backfires as a computer was not installed on the car. It only produces sound. I also have a new Akfa with all its accessories available + 2 remotes. About the exhaust: F1 exhaust system Exhaust valve plate thickness is 4 mm (highest thickness compared to usual valve plates). Benefit: stronger resistance to backfires and revving. Made of 304 stainless steel and TIG welding. Exhaust size is 3 inches. Sound on/off via remote. Akfa for faster air exit, which increases the car's power. A noticeable increase in sporty performance and horsepower. Compatible with most cars.