ISX 870 tuning questions

[Precisionw900]

Hey gents, new to the forum but have been reading for some time. I have an 04 isx 870 with 390k that came out of California. It had an added after treatment system that has been removed. I had my local dealer restore a factory tune but was informed it would be the lastest revision. To be honest they didn’t seem very knowledgeable or helpful. I would like some direction amongst you Cummins gurus on a safe and reliable tune just to make sure it is correct and what do I need to do or who do I need to contact?
Im no stranger to wrenches but machanical motors is what I know so tuning is somewhat new to me. Any information or advice would be greatly appreciated. Thanks