S68 JB4 Tuner for 2025+ G90 G99 BMW M5Gains are 93WHP on pump gas and up to 135WHP on higher octane or E85 mixtures. The ultimate tune for your 4. 4L S68 powered G90 G99 BMW M5. The JB4 allows you to go from factory stock to full race and everywhere in between. The JB4 installs and removes easily and includes many unique features not found in any other tune, including user adjustable 1st and 2nd gear boost limiting, smartphone integration, electronic wastegate control, ethanol fuel