@famousX5 (and experts here) what is your running temp? Is it possible your thermostat is bad? I remember reading that the thermostat going out can cause the lower mpg,wondering if it could have to do with the regeneration thing as well.
Curious myself as I don't generally get more than 22.1 combined, right on the cusp of lower mpg and my running temps were right on the lower end of normal expected as well - it has been months since they checked, sorry don't recall my actual temps).