RENNtech ECU Upgrade | W166 | ML 550 | 480HP / 605LB-FT | 4.7L V8 BiTurbo | M278ECU Upgrade 480HP 605LB FT Gains: +32HP +67LB FT Our intermediate level ECU upgrade for the Mercedes M278 engine still offers huge gains in performance across the entire RPM range, but with a slightly reduced peak HP and torque from our standard tune. This is ideal for customers who want increased performance in their daily driver without worry of extra strain on driveline components or for areas and countries with extreme altitudes, temperatures or