CRDI 2010 Black Smoke By Escape

I'm still having the same problem. I changed the clutch switch and nothing changed. I took the car to be scanned and it didn't show any errors. The mechanic says it must be a faulty injector, which, as I mentioned, I tested on a bench. I told the mechanic about the MAF sensor, and he said that if it were bad, the scanner would have indicated it. The only change I've noticed in the car is that when accelerating, it's like when a gas station has a misfiring spark plug; then it suddenly surges with power, but it blows a cloud of smoke when shifting gears, and it cuts out. If you push it, it emits another cloud of smoke, picks up speed, and then drops to idle. I would appreciate any help before deciding to change the injectors, which are very expensive.
The car isn't consuming oil, and diesel consumption hasn't increased.
Thank you in advance for your response.
Jose

Good colleague could put a mark and line of the car, so I could help you a little more