I SX 2350 regen issues – please help!

[RSCTRANS]

299,000 miles. First The NOX sensor went bad – Replaced. Then the dozer valve went bad – replaced. Removed DPF and DOC and had them cleaned. Next it was the DPF differential sensor – replaced. My DPF system, not long after cleaning, was constantly performing regents until the level became critically high. That is when I originally found this site. I had my DPF and DOC cleaned again. While they were being cleaned for the second time in two months, I performed the EGR tuneup. Re-installed the DOC and DPF yesterday, System began to perform Constant regents again after only a few miles. Soot level is again critically high. I have calibrated the ECM with updates Since the NOX sensor went up. I do have Cummins insight. Not sure where to begin at this point. Should I replace the three temperature sensors on the DOC and DPF? Could the DPF differential sensor I replaced be malfunctioning? Could the EGR valve be bad? If so I figured it should throw a code. Could this be a internal engine problem? could this be a wiring problem? anything I am missing? Where the heck should I start? Please advise of any suggestions on where I should begin. Your help will be greatly appreciated. I am frustrated but not giving up until I fix it myself. I refuse to take to a dealer.