You could replace the useless Roots supercharger with a Garret Gt3 ball bearing turbo. Replace the auto box with a manual, (I have a Geatrag dogleg from a 190e Cosworth in my Clk230k now turbo). You will see at-least 330 ft lbs/torque at the hubs. I had a lot more work done including Solaris motor sport Ecu. lots more info is available if you want to have the fastest Clk230k possibly in the UK
No-matter what you do with your engine you will not get much more power because of the limitations of the supercharger.