It's a thought. I thought your EGT's were a bit dramatic, but it's a 6.7 vs my 5.9. My 08 never had a problem other than injectors compliments of Air Dog. Could be the rail started to rust too. I hated that truck. The seat was the real killer. My 03 is a nicer truck and 5 years older.
The 6.7 smoked all the time. The 5.9 I rarely see even a puff from with a load. But I baby it because of the trans and torque converter. Some day
That said, you may have a soot buildup on the probe. That's why I thought of it
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