What would cause so much smoke to coke from the exhaust like this?

DEF has nothing to do with it. The smoke is from the DPF. Different system.

 

I thought the DEF is what cleans the DPF. Too many abbreviations. Always a bad sign.

 

Nope, heat cleans the DPF.

There's the DOC (the catalyst). Its the first item the exhaust flows through. It reacts with fuel, which is what creates the heat for a regen in the DPF. Further down, after the DOC and DPF is the DEF injector, which sprays DEF into the SCR catalyst.

DOC/DPF remove particulates, EGR and SCR is what reduces the NOx.

 

Lol, I’m really lost now