The turbos in addition to the time should have been enough for 630HP by itself without the others components. Depending on how your water methanol injection is ran I’ve seen my buddies make 50 - 100HP with that also. Bottom line is these guys screwed you and need to have a sit down with management.

I’m looking at your dyno sheet and the number look suspect to me and here’s why. I have a CLS63 2014 AWD which loses more HP on the dyno than RWD. My car has nothing other than a tune and I’m still putting down 584hp with 696tq. With turbos your numbers should be blowing mine clean out the water. I would definitely assume that it’s the tune. If you want the most aggressive tune i would recommend Euro Charged. I decided to roll with Renntech because it doesn’t void my warranty. My friend has a 2015 CLS63 AWD that’s putting down 630hp and 750tq. He has air filters and a tune so I would say you definitely have a problem.

Wow man, “scratching my head”. I’m not sure what the deal is if your ECU was flashed by Eurocharged. This is something that will have to be picked a part by a master tuner/technician. If you have a reputable shop there I would have them to go through everything with I fine tooth comb. Even the serial number on the turbos to make sure all the hardware is what it’s suppose to be. Especially with the water methonol system because if the line are wrong coming off the pump on the tank the system will not perform properly and possibly grounds for detonation. But that’s all I can think of seeing how you have already retuned the car multiple times with little to no results. For what it’s worth I’m really sorry you’re dealing with this madness knowing that you’ve paid top dollar for premium service. You’ll just have to put your foot down and be firm with these guys because you want results NOT excuses.