I'm looking in to this as well, and found chip tuning to be a pretty standard performance upgrade.
Try looking for a tuner that has experience with the A-class 180 or 200 which is the exact same engine.
I read the standard upgrade is 122 - 156hp and 200 - 250 fpt, to your 180 will turn in to a 200 just like that!
Some tuners will (for extra money) take over your factory warranty.
And, if your afraid the mechanics will bitch about the tuning, you can use a tuning bypass module, which you can take from the original wiring when you turn it in for service.
Actually, my Dutch dealer is perfectly okay with this method of engine tuning!