You are running an M102 motor and its only slightly different from the M102 motor in the 190E 2.3 here in the US (I believe the bore and stroke sizes are slightly different). The 230E was not sold here so hardly anything here has been built to enhance its engine. You might want to check some of the European tuners who have cam kits available for it. Like every other Eclasse the money to power ratio will be hard on your wallet. Your best bet is to trade up!
The 230E/TE is an awesome engine and it will last you for years. I have people who drive mine here in the States and swear its a 6 but it does feel under powered sometimes under load. It would be interesting to hear what some people here have to say but, I say live with it!!

Just my small opinion thats all...
yal 88 230E (w124)