There is a huge variety of turbo components and their combinations.
It all depends on what you want and how much you are willing to pay for
it.
Not all goals can always be met though. So usually the selection is
a compromise. But sometimes one can improve both maximum hp potential
AND low end boost /response by changing to a different turbo.
Someday when I feel inspired I'll write more on this subject ;)
For now, here are some links to companies selling turbochargers:
