What is the difference between the JB+ and the JB4?
The JB+ features a faster install and does not require you to touch the ECU. The JB4 is a more robust system including steering wheel control map switching, direct boost solenoid control, throttle position mapping, and many other additional features that allow it to produce a lot more power. On average the JB+ gives 40hp to the wheels, while the JB3 gives 70-80hp to the wheels, on an otherwise stock car.
