62.5 stock if memory serves me on the 800. When I added a slip on exhaust to my Wildcat 700 (60+ HP, AC never revealed a solid # altho the consensus is it has 64), the manufacturer claimed 9% HP gains, which would put me around 70hp. That's without a tune, so I'd guess 71-73 for the Z800 with an AFR tuner in place.
I'm curious how easy the Dobeck is to dial in compared to the Power Commander's autotune feature that requires another bung being added to the header for AFR measurements. That's my only concern when you add a tuner - you start down that rabbit hole of maintaining the perfect AFR to keep that motor humming along nicely.
I can tell you one thing, that Rotax 800 sounds a LOT better than my 700 when you open it up. Always loved the sound of a Rotax twin doing what it does best !