X15 1659 Code

[Therealarw]

Hi Guys I have a Cummins X15 X114B giving me some injector issues. The truck runs and idles fine, it has plenty of power but I will get the message of it saying it that it's going to do a 25%
derate. The injector is brand new from Cummins, and it keeps wanting to regen so I'm also trying to see if there's an exhaust leak somewhere because I know that when these motors don't have constant exhaust pressure it'll keep wanting to regen. The only code I'm getting though is just a 1659. So far I have ran the rack and checked all the lobes on the camshaft and everything looks good. The truck has 400,000 miles on it. I'm only getting the #6 injector while all the other injectors are fine. Kind of confused because Quickserve doesn't really give me too much info on what I need to do as far as troubleshooting. My last question is it even possible to get an Injector code from an exhaust leak because of it wanting to regen? Thanks for the help!