Z4 Boost Controller keep the roadster tradition alive. Adjust your turbo's power with a Boost Controller. New Z4 Boost Controller add to the performance BMW provides. Choose the amount of boost with the Boost Controller for the optimum setup. Add a little flair to your Coupe with new Z4 Boost Controller. A Boost Controller is easily adjusted and easily installed. Make your engine the best it can be with a new Boost Controller.