Originally Posted by gsxr

In case anyone missed it, the solution was posted in a PDF file back in post #11 on this thread. Straight from the factory Mercedes documentation. I didn't hear it from by sister's best friend's brother's second cousin who saw it on Facebook on their phone. I confirmed it myself, on my W210 1997 E420 on the dyno. It works. Don't re-invent the wheel.

For those wondering, no, pushing the "ESP Off" button on the console won't work. There will be an engine rev limiter which prevents going to redline. The system MUST be fully disabled as described in the PDF in post #11. The "ESP Off" button should really be labeled "ESP Mostly Off", or "ESP Off with Side Effects", but I guess they figured the font would be too small.

As to the guy selling the software upgrade trying to tell you don't bother with the dyno... that would make me even more intent on the dyno results. Sounds like he's hoping you never find out the measured power gain is below what they claim. Only one way to find out. The "too many variables" is a bluff... the dyno system will automatically compensate for weather conditions. You'll need to make sure the engine/trans is somewhat similar temperatures and there were no other changes since the previous run (i.e., same wheels/tires, no other mechanical changes/upgrades to the motor, etc).