Passenger Side Black smoke exhaust

[loush]

Hey All I hope every body is fine and safe...

So i picked up a nice 2011 X5M in a supper condition except for the black smoke which as far as i knew it was a bad injector no.4, Did that changed it and along i changed a full spark plugs set and a set of coils, the car performed much better and feels healthier.

Sadly the black smoke is still there when i put my foot down and I get a big puff as i change gears on woot.

Any suggestions?

If its cats should i get 2 performance downpipes