Yeah, but it's not the speed limit: if you are exporting the car they used to have quite stringent regs about what you may and may not do on the special export plate. There also used to be an issue that the manufacturer can be liable for certain things done by the exporting driver as they have to request the plate to be issued: this means BMW might simply dissociate themselves (and possibly void the insurance) in the event of say, a crash involving another vehicle.

I also don't think you can just get into a car in a foreign country with different road regulations and usage patterns, gas it up to 180 mph and expect to get away with it without getting into a crash. Other drivers on the bahn will expect you to stick to the "rules" (ie. lane discipline, etc.) that they expect. Driving at that speed after you have been only used to the double nickel or 75 mph speed limit is something completely different.

I simply wouldn't do it, and you would just glaze the engine bores anyway (no matter how well made it is) which will lead to increased oil consumption in the future. The whole idea is just a mess of problems waiting to happen.