Tanksoldier,
I am having the same issue with my 6.0L. I have not taken it into be fixed, however I have talked to a Good / Highly Recommended Dealer in my area. You can have one of several issues causing the same problem. The obvious one is the sensor had failed, which means you replace the sensor. The wire chafing issue that Mike talked about, a wire/s that have rubbed and now have a bear spot shorting out. Do you have an oil leak from the back of the engine? The sensor could be leaking, or the fitting that the sensor goes into is leaking. Mine is leaking, it is a very slight drip that has not even registered on the dipstick. (The full to add marks on a 6.0 is 2 QUARTS) This leak can get oil into the electrical connector causing the sensor to not communicate. There is a pigtail they replace to resolve the chafing or "wet" connection issue. I have been told by a dealer (NOT the one that I am going to use) that an ICP replacement is almost $500 (Which I believe is what the book says). The recommended dealer that I am using told me that is worst case, as the sensor is expensive, the other problems are fairly easy to fix and the parts are not very expensive, could be as little as $150. I have been driving it some, and I see some of the issues that you are describing. Fixing the issue with the sensor should cure that... the ICP controls the engine idle via the HPOP. Also one other problem besides the ICP that can effect the performance is the Routine maintenance. Make sure you change oil at 5K and the Fuel Filters at 10K and I would use only Motorcraft Filters. I can feel a definite performance change between a new set of fuel filters and one that has 10K on them. I would ask around an find a recommened garage that is QUALIFIED to work on the 6.0L. Just because it is a Ford Dealership doesn't mean they have anyone trained to work on the 6.0L. I am actually going to drive about 70 miles to the dealer I plan on using. If you do plan on changing it yourself I have heard that it is accessed from the bottom, I have seen on SDD that someone saw a tech at a dealership replace it from the top. I have only looked from the top and I am not sure how to get to it. If thery were and 04-07 the ICP was moved to the front of the right head in the oil line, like the 7.3 had, the left rear was an 03 only thing. I hope this helps and I am sorry for the long post. I hope to get mine in, in the next few weeks. I will post the results back when I have it repaired.....