Power loss at "take off" ('95 S320)

[sab]

I have an unpleasant condition, where my S320 has no power at "take off" from e.g. a traffic light. Once I completely depress the throttle (WOT) it has full power.
The car runs completely normal when it is cold. Once it is warmed up, especially when I shut it off and then back on, it starts to have an intermittend surging idle and this pesty power loss.
When I got a read out from the check engine light a while ago it indicated the O2 sensor, I changed both O2 sensors and the condition persists.
I reset the check engine light after changing the O2 sensors and the light came back on.
What could this be? MAF sensor? Vacuum leak?
I tlooked for vacuum leaks, but could not find one.
Where can I get the codes read out from my check engine light? Or should I buy the tool?
Thanks,
Sab.