Z 1000 / ZX9R Bottom end Butterflies

Just wondering if any one has remove the butterflies that restrict the engineat low revs on a ZThou or ZX9R?
They have done it at mid town on a shop Z750and one of their employees Z1000. It is to increase the 'snappiness' of the bottom end.
My main query is whether it leans the engine out to far and cause other issues. They have said it won't affect my warranty etc but i am still sceptical.
Thanks
Terry
PS pls reply with factual personal experiences with your own bike. Comments on the dealership are not necessary.
They have done it at mid town on a shop Z750and one of their employees Z1000. It is to increase the 'snappiness' of the bottom end.
My main query is whether it leans the engine out to far and cause other issues. They have said it won't affect my warranty etc but i am still sceptical.
Thanks
Terry
PS pls reply with factual personal experiences with your own bike. Comments on the dealership are not necessary.