No regen because of low temperature

I have a 2016 Cascadia with DD15. Shows high soot level. Started parked regen. DOC and DPF temperature won't go above 385*C (if I am not mistaken dosing doesn't start until 400*C, right?). Could it have anything to do with "SPN 102 FMI 16 - Intake Manifold Pressure High" code it has. I tried replacing the sensor, but the code didn't go away, it shows as permanent. I checked the pressure, when idling, ~1.5psi above barometric, @1500RPM ~3.5psi higher.