Just a reminder the M157 is a torque monster - Eurocharged tuned Mercedes C216 CL63 AMG tops 784 lb-ft of torque at the wheels
The M157 5.5 liter V8 may be getting phased out by the M177/M178 4.0 liter architecture but that just means the M157 is becoming an increasingly great AMG tuning value proposition. Just look at these ECU tune only figures from Eurocharged form a C216 CL63 AMG.
Yes, ECU tune only:
154 lb-ft of torque at the wheels picked up. At 3644 rpm the difference is a staggering 170 lb-ft of torque. Night and day does not even cover it.
The torque curve levels off toward redline so the peak horsepower increase is not quite as massive but this motor is all about the low end.