Thanks to all who helped solve my problem. The culprit turned out to be the dreaded wiring harness. I Zeroxed a hand full of the threads from the archives and went into my dealer. Even though the car now has 150k miles on it, the dealership picked up the cost of the harness and half of the labor. So, I ended up paying for about 3 hours of labor. In the end, it was a great decision to let the dealer change out the harness. In ordering the new harness, they ran into a batch of harnesses that were in the correctly marked package, but which were not the harness for my car. Only on the fifth try did they get the correct harness!
Once installed, the car ran much better, and has picked up almost 5 mpg in fuel economy! I am still getting the code 5, indicating an issue with the EGR, so, I'll find time to perform the vacuum test on the valve and then "attempt" to clean out the EGR pipe.
Again, thanks to all.