There are a few things they did to make the car be "not quite an SLK320", like rate the engine at 215 hp when, in the '320, it delivers 230 hp.
I have never understood if the RATING is different alone, or if they really did tune it to 215hp.

As to the radio problem, I have driven mine across country twice (I now have 97000 on it) and have never had the radio jump in frequency like some people say theirs does.
I attribute it to a setting somewhere in the radio, which invokes a scan function - but other than that, I have no clue. And I've been in radio for 30 years.