Ok so don’t really know where to start here. I got a good deal on a 2012 3500 truck obviously has some work but no real idea what. Runs great pulls great studded deleted a little smoky under hard throttle but not bad. Trans shifts better than any other 68 I’ve ever had tuned or not. First question anything in particular to look at for hints as far as to what may be done as far as possible injectors pump work trans work etc. I can see where at one time there was a 5 position switch but can find no other evidence of a tuner currently being on the truck. I’ve looked all under the dash and hood that brings me to my next question. It has a couple of stored codes that seem to could possibly be caused by deletes and no tuner. Current codes are p-0602, p-0191, p-040c, p-006f. I’m not new to Cummins just have never came behind something someone else has had their hands all over