What's wrong with the stock turbo for 500hp?
Yes you can get 500hp out of the stock turbo, but you have to drive it very hard and frankly it's harder on the motor pushing a turbo out of it's efficiency range. If you want to drive around all the time on a 500hp tune I would suggest getting a turbo or upgrading the IHI which is also a great option.
Not correct. Remember....you arent at 500hp in every gear, all the time. It'll only be 500 at WOT....do you drive at WOT all the time????