30hp is a bit of an exageration on that exhaust. Fact is, there isn't too much you can do after the catalytic converter flange to add that kind of hp. If the Lorinser is just the muffler section, you may get an extra hp or two.

As for the ECU, your CLK is high tech, and the engine will need to be re-programmed to take this in. These cars are a little trickier to tune.