95 Cadillac Sedan Deville P055 Code

Have a 95 Cadillac Sedan Deville, 4.9L, that has a P055 Current code.
So far I have replaced the TP sensor, ISC motor, MAP sensor, O2 sensor
twice and spark plugs. I also removed the throttle body and cleaned it. I have performed the idle relearn procedure,
set the ISC motor screw position, however what I could find on the
internet was for a 94 cadi w/ northstar and 4.6L, which called for the TP Max
minus the TP min value to be between 10 and 11, don't know if this is
correct for my model. Also RPM's when in park are 1350-1450 and when in
park with brake on 950-1050. When car reaches about 8mph it want to
take off. Had car hooked up to computer at garage and said that the fuel
was to rich at O2 sensor on the replaced sensor. I am my wits end is
there anything that I can do or does it need to go the garage and have
problem traced.