ecm going bad?????

After lots and lots of time at kw and cat and lots of parts thrown at it for a fuel problem . My cat messenger is reading 4.xx mpg bobtailing or loaded and its saying Im using 700 gallons when I used only 400. I counted up my mpg and Im getting 5.7...still not where it was before the fuel problem.The messenger has been close to accurate for 10 yrs. 2005 kw w900 mxs c15. It has been a little bit low on power and mpg. it still builds 57 psi of boost. And it gets 115 psi at 1800 rpm for fuel pressure.

 

cat and kw tested them with the cat et and they say they say that they are all ok. I was wondering if maybe they are not flowing correctly or if there is a way to even check that?