ISX cm2350 low. power/poor. Fuel milage.

[DPS567180]

Okay I think I found my issue. At the very least this is an issue. I did a parked regen today and when I looked by the exhaust there was white sit on the ground and residue on my tailpipe. I immediately thought it was my DEF injector failing again but when I checked it there was no crystal build up and I have a little cheap borescope and there was no sign of buildup inside the decomposition chamber. It's not coolant I've done a pressure test and I have no loss so I don't know what it could be but I'm assuming this is a problem.