CM871 Slow Climbing Regen Temps

[Taco05]

I have a 2009 ISX and the Filter IN and Filter OUT temp take more than 15 min to reach 900F. Egr valve has been replaced before, both Delta P sensors are new, Imap and Exhaust pressure sensor are also new. Also new Doser installed a week ago. I have checked all the tubes to the Delta sensors and cleaned them as well. DPF filter and DOC have been at Cummins for cleaning 2 weeks ago and both passed. The truck is asking for a regen almost non stop and when I do a forced regen it smokes quite a bit but there is no oil or coolant consumption. Aftertreatment diff pressure stayed between 2.5-3.5 inHg during the last Regen but history showed 8-9 inHg pressure for previous regens.
Truck is doing a run right now should be back at the shop in 2 days and I will check the aftertreatment history for frequency of regens and diff pressures.
Any Idea what else could cause this non-stop regen request, slow temp climb and high diff pressure? I was leaning towards a new DPF filter even though cummins said it passed inspection and cleaned out good.