[Turbod]

The stock flash will start to reducing timing advance and introduce more fuel to richen up and cool the combustion temps. The JB4 doesn't alter any of this. Without logs it is hard to speculate as to what is causing a surge. You should feel reduced power as the IATs climb that high. I would install a methanol kit if I were you. The stock intercooler will still be an issue but methanol will slow down the rate in which your IATs are climbing.