1994 e320 revving high
 

I have a 1994 e320, I had a problem with the idling, it used to rev up and down.... i changed the spark plugs, wires, mass air flow sensor, some vaccuum lines. but now the idle stays high. i tried adjusting it, but it stays the same. in drive its at about 800, and in park it settle at about 1200 or 1300.
it used to be in drive around 500 and park 700.

I read the codes i got:

code 6 in the built in reader
code 8 in pin 8
code 2 in pin 14

any ideas?

i want to add that when i initially had the surging idle, i did play around with the throttle cable and and connection at the gas pedal.