So you actually mean you "cat walked" the bike from a first gear power wheelie all the way out to 6th. You don't need power to shift while holding a wheelie, just great balance and throttle control. Power wheelie implies you are actually bringing it up in 6th gear without using the clutch, just the throttle, in which case you need a whole shit load of power (this is where the turbo would come in).

I would be really careful shifting while doing wheelies if you do not practice stunts on a regular basis... lots can go wrong, especially when you don't even mean to bring the front end up in the first place.

If you did it on purpose, congrats... I am sure it is not easy to do. I am still too chicken shit to even try 1st to 2nd.