I bought an '03 CR Cummins from a guy that had used a programmer. After the test drive and purchase, I noticed a light (but annoying) amount of black smoke out of the exhaust at idle. There is a light rattle (sounded like 2nd Gen) under load at hwy speeds. I checked the injectors (disabled them individualy) and the truck still smokes. Does this sound like an ECU problem to anyone? Got the P 0602 code. Is it possible there was an error when the truck was returned to stock performance? Otherwise, truck starts and runs fine. Thinkin maybe affected timing. Let me know