I just went through a nearly identical problem on my 97 7.3. Final result: $535 with a new $180 ICP Sensor. Runs like a champ. I tried everything suggested including pulling the ICP for cleaning and o-rings, new CPS, GPR, Fuel Filter, Oil and filter change before taking it to the shop. Good luck. PS you can find a new sensor on E-bay for $70 +\-.