Hm ok I guess this was something complete strange on my vserver. I stopped b3. Disabled all plugins except admin. Started again. Result was a cpu time of about 30%. Better than 70% but still very strange so I completely restarted the vserver. Everything is nice now. Cpu time of about 0.2% is quiet nice. I still don't have a clue why this happened, but it works now...

Thanks!