It sounds as though you have a decent overall combination at this juncture.
What is the longest duration you've run at full power?
My guess is that the heat rejection limit of the cooling system would be the time limiter.
Is your fueling system strictly a PC along with the ECU?
No ignition retard at all?
No fuel pressure boosting?
#1 I have ran it at full boost in every gear (trying to keep the nose down). I have rode the bike 200 miles in one day without issue of overheating. I constantly monitor the digital dash combo gauge built into the Aim MXL display. I have never had an issue with cooling. Remember that in a real life scenario you are not boosting all the time your moving forward... In town I just tool around like any other day on a 919. This is my daily driver weather permitting and never has it gotten hot. This is a mild build on stock internals- stock pistons.
#2 Fueling is not stock. Has a secondary Walbro fuel pump, aeromotive fuel pressure regulator - boost compensating - 60 psi base. PCIII with hub and ignition module although I did not find a need to retard the timing as it yields no gain on the dyno.
Garrett GT25R ball bearing turbo - internal wastegate - currently set at 8psi
custom oil filter relocator
K&N air filter
304 stainless manifold and exhaust pipe
RB racing oil evac pump
Jegs AN Fittings and braided stainless lines
walboro fuel pump
aeromotive fuel pressure regulator - boost compensating - 60 psi base
Fabricated aluminum plenum
fabricated stainless battery basket
PC3 with ignition commander and hub with boost compensation
rc51 front forks, cbr 954 rim and brakes
Aim MXL display with AFR, boost and EGT, mph, temp, oil pressure, RPM, and alarms
*Disclaimer- I did not build this bike from scratch. I bought it from a forum member who does not visit here anymore. He built this set up in 2009 and has ran the bike over 25,000 miles with the turbo installed (so ya, not worried about "heat rejection limit of the cooling system" being a problem- its proven solid) When I bought it I ran a compression check and found it was down about 15 psi from my other 919 with only 5k miles. So I decided to swap everything over to my red 2006 919. In doing so I replaced every o-ring, gasket, seal, vac and pressure line, and remedied a few electrical issues. I decided to make a few improvements along the way to benefit what was already there. I returned the black 919 to stock-ish and it runs and drives great.