The thing is, there are two scenarios here, one of which is potentially costly to the owner.
1) The dyno figures are grossly overstated. Sneaky marketing. The car will actually be making around 170-180 with the map, which shouldn't be harmful to the car assuming certain parameters are kept in check. This is usually around the power level a BKD will reach with a good map.
Or...
2) The car is actually making 200+ bhp, with standard hardware. A mapper could theoretically force the car to make this much power, with huge boost, silly timing, all the rest of it. But the turbo would last 5 minutes. Literally. The thing would just self destruct.
I'm guessing it's closer to 1 than 2.
Celtic Tuning were notorious for overstating their bhp claims on the old 1.9 diesels. There was quite a flap about it at one point. Looking at the website it seems they're STILL at it...