RENNtech ECU Upgrade for CLS 550 | C219 | 402 HP / 405 LB-FT | M273 BiTurbo | MY2007-2011RENNtech ECU Upgrade for 219 CLS 550, up to 402HP, 405LB FT. Gains: +20HP & 14LB FT RENNtech M273 Biturbo ECU Upgrades RENNtech HHT (hand held tuner) allows you the unlimited ability to switch between tuned and stock ECU programming and requires no ECU removal! Our proprietary tuning module stores both the RENNtech tuned file and your vehicles stock file. The module plugs directly into the OBD2 port and delivers the file you choose directly to the