I recently had to replace the intake manifold on my '96 Town Car. The original manifold was replaced at factory expense due to the class action lawsuit over the water crossover cracking. THAT manifold 4 years later developed a crack at the passenger rear and was leaking water near the heater outlet.
The people that did the work (I only do minor stuff on daily drivers) said they had cleaned out the EGR tube because it was clogged up.
This was last month and I'm here to tell you that in spite of colder weather, I am getting .8 MPG better.
This sort of reinforces a few points about modern factory EFI and emissions that has been brought up in the past.
Basically, the ability to dial in a bit more advance because EGR is being introduced to lower combustion temperatures causes not only less emissions but better gas mileage.
And this doesn't just apply to Ford engines. I remember reading about the LT1 engine when it first came out and Chevrolet basically said the same thing.
If any of you are thinking that you are going to be daily driving a car you are building, I would seriously consider using a factory EFI system that you can tune yourself to take advantage of the built in engineering for both emissions and mileage they represent, and avoid ripping out ALL emissions stuff.