IF you are going to be pulling in all 4 gears and then expect to keep going in 5th, you better have that thing tuned perfectly, and then a little rich on top of it. Heat soak is bad. I will go out on a limb and say the power level you were at had little to do with the failure, and heat soak induced knock had everything to do with it. Even on my car, which is a pretty well setup car, I would never pull all the way into 5th gear.
My engine would probably survive the knock unlike a motor that wasnt setup for turbo, but it would still make me cringe.