Isx cm2250

[Hammerhead]

You did not state the model, mileage, etc.
I'd also get a bypass filter installed on that thing, like last week!
Perform an EGR tune up ASAP. Since it's used, it most likely has never had the sensors related to this changed. Don't bother cleaning them, replace them; Imap, delta-p (EGR diff press for intake, not DPF), exhaust gas back pressure sensor, remove and inspect the doser and be prepared to change it as well.
Run an overhead adjustment, and carefully inspect the cam and rocker roller followers while you're in there. Too bad you hadn't posted this a few days ago, I was hangin out in vegas, I could have taught you to run the O/H adjustment. I pack the tools with me to do it. All you need for a 2250 is an in/lb torque wrench with a 13mm crows foot, a ft/lb torque wrench with a 19mm crows foot, and a feeler gauge (with .014, .027(if it doesn't have this one, you can stack the .013 & .014 to make .027), and has a total of .276. As well as a 3/4" drive ratchet with a short extension.
That's your starting point.
If you intend to own this truck for a while, find a Chinese knock off Inline 5 datalink adapter with Insite 7.6.xx they're about $400 on eBay.
Oh yeah, I case you didn't catch it, read A LOT on this site.