2006 Mercedes Benz C230

Engine Performance problem
2006 Mercedes Benz C230 6 cyl Two Wheel Drive Automatic 120000 miles

Hi I have a 06 C230 120K miles, I keep it well maintained but recently had problems.
The mechanic I go to is baffled, I have the codes of P0171 P0174 bank 1 and 2.
But the problem is start the car no issue, then tap the accelerator and the idle will jump to 10K+ and stay there, kick it hard and the revvs come down to normal 5/800. If you leave it at 10K it will climb to 20K and then return on its own to 5/800 with a bad idle!

I just cleaned the MAF this made no change at all.
Any ideas or suggestions?

Thank you
February 26, 2010.

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