This product is designed without a rear box and will be loud. Requires mandatory ECU reflash.Cobra Sport performance exhausts enhance the sound, looks and quality of your vehicle giving you the ultimate driving experience. Our sports exhausts range is fully guaranteed to give you assurance of our quality.This Ford Focus ST Estate Mk4 cat back performance exhaust is made in 3"/76.2mm pipework and fits from the Catalyst section backwards (Cat-back) replacing the GPF, centre and rear sections.This sports exhaust is part of the Cobra Sport Venom range and is loud.IMPORTANT: this exhaust removes the GPF filter and will require engine tuning at time of fitment to cancel the EML light.Fitment to GPF equipped models is for motorsport and off road use only and will exceed noise regulations.Cobra Sport Exhausts provide the performance exhaust solutions for the Mk4 Focus STs raced by the MB Motorsport accelerated by Blue Square and Motorbase Performance teams in the 2021 Kwik Fit British Touring Car Championship. This technical partnership allows us to test our products on track at the highest level of British Motorsport. The experience gained from the competitive track environment is fed back into all of our road going performance exhaust systems.