WILL I BE THROWING MY MONEY AWAY?

[BLOODSWEATTEARSMX13]

I am facing a dilemma. I own a 2013 587 Pete with a 2102 first generation series MX-13. The truck will not regen unless I force regen it with my OTR Reset Tool. The truck is in power loss but it's not horrible power loss but it gets horrible fuel mileage. I ordered tru balance centering sleeves, new Monroe magnum shocks air tabs, a fleet guard air filter, an oil purification system and cat's eyes to help increase the fuel mileage. The rig has had a new differential pressure sensor, dozer injector, turbo, fuel line and egr valve replaced in the last 8 months. The DPF and DOC have been baked and all sensors on them replaced in the last 4 months. My question is if I replace all sensors(IMAP, NOX, Diff Press Sensor, dozers etc...) and do not replace the DOC, DPF, SCR, decomposition tube will I be throwing my money away? Is it possible to just replace the decomposition tube (I have heard from mechanics that it gets packed with DEF crystals) along with all sensors and dozers, have the motor and charge air cooler checked for any leaks and replace anything causing pressure loss which would undoubtedly correct most of my fuel mileage problems. Do I have to replace those cans? The truck currently has 657,000 miles on it. Any suggestions would be appreciated. Thank you