SAI pump question

So I did the leaking pump fix, and it's now a lot quieter. Before I fixed it the car was a bit lumpy/hesitant when sticking the pedal to the metal. pump is now fixed and it runs as smooth as a babies bum. How is this possible? I thought the pump was basically off after it did its initial startup job, but it is 100% smoother under acceleration. I hope it doesn't go back to how it was before, but if you believe me, can anyone explain why this is?

Dan