The M157 responds dramatically to tuning, and 700hp is described as easy with intake, exhaust and an ECU flash; a documented Renntech R1 build reached 696hp and 801 lb-ft. Owners cite over 750hp with modest work, and note Weistec is favored in California for making power on lower-octane fuel.
Tuning headroom: Renntech, Weistec, and 700-plus horsepower
Mercedes-Benz E63 AMG (W212) · mechanical