Have Been Scolded By Mechanic in the Past
Although, I own a diesel MB I do have an American vehicle with fuel injection that I had added injection cleaner to the fuel tank, and ended up with the same results as you describe. Luckily is was still under warranty and I pushed my own made problem off on the dealer who kindly informed me that I had used a cleaner and although I though I purchased a quality cleaner it actually just dislodged the garbage that either clogged the injector, causing the rough idle or did little good at all. They of course used a high dollar cleaner to dissolve the crap I dislodged in the system and all was fine after they ran it through the engine. I guess the moral of the story was one of the following. Don't fix what isn't broke, and if you decide to anyway, spend the money on the right product, otherwise you just create yourself more headaches.