Is your mpg down like in the 12-15 mpg range and are you seeing black smoke out the exhaust? Went thru an identical fiasco with a 96 850 with the same codes. Turns out (1) had a vac leak and (2) recv'd the wrong 02 sensor followed by a defective sensor from a vendor. The front sensor was responsible for the codes and when we finally got it right, the car has been prefect ever since. Are you using Alex Peper's software? If so, configure your #1 gauge to read the voltage for the front o2 sensor (bank 1, sensor 1). Start the engine and watch the voltage. It will fluxiate quite rapidly in the .25-.75v range if the sensor is good.

bl