I've been running b100 and just had my first hiccup problem this weekend towing to windrock. 2006 LBZ with 160 gallons through it.
Last time I filled up, the tanker truck was filling up the tank stirring up the sediments. I didn't think anything of it.
I used a wix filter that had maybe 3000 miles run through it. I've now understood they quality of the duramax wix is not the best.
Towing down through hot springs I downshifted often getting the motor the hottest it's ever been since I've owned it. U haul hydraulic trailer brakes are all or nothing.
When it flattened out in TN I noticed an audible knocking between 1000-1700 RPM and rough idle.
Never lost power and made it to camp. Next day it took 7 tries to crank. Never drove it. Day after that cranked but had a rough idle and the knocking was still there.
Got it into Oak Ridge and changed fuel filter and added some diesel Kleen to a fresh tank of Exxon diesel. Also noticed black fuel around the fuel sensor.
Drove back through the I-40 gorge and the knocking drastically massaged its way out.
Apparently Wix duramax filters are not the best. I've thought about doing the CAT fuel filter modification.
Driving to work today and it's smooth as butter. To @jeff_b point the filtration is key.
My only thought is I over heated the fuel and it gelled? I don't understand exactly what I did but the truck runs fine now.