Low EGT's 250°f wont regen

[AyronP]

How's it going yall?
So I have this 2012 isx single cam that won't regen, I've been all over this truck, reman turbo, fixed a bunch of exhaust leaks, lots of back lash in the idler gears. It just won't get hot, and low exhaust pressure as well. Most of our trucks read 150inhg
When in regen but this one won't get over 40inhg. It had a 1921 code but when I blew out the dpf it actually went away on the drive back to the shop. I'm stuck.[/size]