Why would the PRO-M 80mm make soot?

[NEILL93SHO]

I have gone back and forth with the 55mm and 80mm pro-m. The pro-m does give me stronger pull through the gears (butt dino?) but within a day or so i start to see some soot around the tail pipes. The stock brings me back to clean and wishing the 80mm worked better. Any Ideas?

 

[Mr Anonymous]

Only way to tell for sure is to get your car on a dyno with an a/f reading to see the difference between the two. Are you getting a CEL with rich O2 codes when running the Pro-M?