About a year ago, I had my '07 ML CDI go into "Limp Home Mode" where you get very weak acceleration, and maybe a shift up to third gear. You should also be seeing the "check engine light".
The dealer was able to fix by replacing the fuel pressure sensor, which was intermittently indicating a high fuel pressure.
If you switch off for about 10 or so seconds and restart, it might go back to regular mode.
And yes, when running right, this thing will launch hard.
