With my setup, what should my fuel mileage be?

[2004F250XLT]

I have an early 04 with 228k miles runs perfect no issues 265/75/16 tires and 3:73 rear. With the cruise set at 65mph at around 1800rpms, what should my mileage be around on the highway? Has 4inch tb straight pipe, blue spring fpr, and running sct performance tune for now. And how much more should it go up with the egr blocked off? Thanks

[dhanna6powerstroke]

I have pretty much the same thing and average around 20-21 on the highway.