RJWC Tuner with CableTuner with Cable If you want to optimize your engine's performance and prevent damage, then our fuel tuner is a must have. Our EFI tuner is recommended for use with any of our exhaust systems to ensure the correct air to fuel mixture. Running a machine with a lean mixture can cause severe engine damage, and that's why we always recommend using our fuel tuner to ensure proper engine operation. A proper air to fuel mixture is essential for the best