2014 Q5 TDI, real bad exhaust smell

[Aaron B]

I have a 2014 Q5 TDI (USA) , 131K miles. Seems to run fine, good power. No error codes on starting or when running. Problem is the exhaust smell is real foul for the last 6 months or so. It even seeps into the cabin at times. Much worse than when I bought it 4 yrs ago. I have been using R-99 biodiesel blend. Could it be a clogged DPF or maybe the fuel itself?
I did have the fuel filter replaced at 119k miles.
Any ideas?

 

[oilhammer]

Look for soot around the top of the engine where the EGR pipes are.

 

[Aaron B]

I will check it for soot and advise. If there is soot, what would this indicate?

 

[oilhammer]

An exhaust leak.