CM 871 getting 3.6 MPG

[Steel Dragon09]

Picked up a 2007 Volvo VT800 in July. Has an ISX CM 871 500st stock motor and after treatment with 200,000 miles on it. I did a few things with the EGR system right away.
1. Baked the entire DPF for around $400. Paperwork showed a flow of 1.0 afterwards.
2. Replaced all sensors on Filter.
3. Replaced- differential pressure sensor on the horn. Imap sensor. 4928594 pressure sensor.
4.Pulled off and cleaned out the horn.
5.Pulled off and cleaned out the 7th injector.

The motor does have to work though. Its hooked to an 18 speed with 3.73 ratio rears and grosses about 117,000 with every load. No real hills. She can still average about 60 mph per trip. She wants to REGEN about every 230 miles. Oil temp stays around 210. She blows white puffs at a steady rhythm in the beginning of the regen and then slowly clears up until the regen is done. Regen takes about 40 minutes on the road.

I don't hear any air from the charged air cooler. As I am writing this I realize I should get it professionally checked. Assuming it is not the charged air cooler what steps do I need to take to get the MPG up? I know I pull heavy but 3.6 mpg is a killer and I feel something isn't right.

Sorry to be so long winded but I got to figure this out.