Either I am unable to communicate well, or you are putting words in my mouth.
Let me try this once again.
By going leaner, the car should have picked up a little power. That means in the past tense. After you made the changes that you did, the car should have picked up a little power. Whether you wanted more power, or not, is not the question...it is just a fact.
Now, you also said it is blowing less black smoke. To me, I took this to mean it is still blowing some black smoke so this would indicate that the car is still on the rich side. Therefore I said you could take it a bit leaner-meaning it was your choice. This was to try to further reduce the black smoke.
Probably, I should have not bothered to comment but sometimes I don't know when to stop...but now I do