Help, power problems

Hello everyone, I have an X5 with 228,000km and the other day I left lying, I have changed the diesel pump and now what I notice is that it has no power, literally, it dies, it is difficult for you to recover in all the marches and throw a lot of black smoke, they tell me that it can be of the air flow sensor, you can tell me where it is located to be able to clean it or change it, I have not been able to see it. All the best