I just got into 4th gear there, and 6krpm is my peak torque (~520wheel torque). I have similar gearing as well, and I believe Z4M hits that crest at around 80mph? I've seen a few Z4Ms shift into 4th right after the crest. If that's correct, powerband on z4M at 7600rpm? in 3rd is about 190wheel torque to the wheels. Big difference
No doubt the rear end got light over the hill there. I probably had 10 degrees left steering wheel input. That combination is lethal.
After the bowl, I'm sometimes on full throttle with about the same steering wheel input, never get loose, but there is not crest on that side.
Going to 5th there could help but it wouldn't make sense to be in 5th through the bowl, too low of a rev and below my boost threshold range unfortunately.
I think I just have to let off slightly just as I approach the peak, then get back on it. I noticed a few other high powered 911s are doing same thing as well.
My lesson for that day is to take into account any crests or hills on the track and be mindful of power application and steering angle. I need to also get a camera further back to study my steering wheel angle for better review.
ANOTHER thing: I wasn't 100% throttle, I was feeding it in trying to be "light" just incase I had to pull back out. You can see my TPS % is below 100%. Unfortunately, like I mentioned, 55% and above essentially guarantees full boost. In other terms:
35%-45% I can modulate 0-12psi. 50% throttle the turbo runs wild and wants 23psi. I wish I can control 14psi-18psi with throttle but it requires a lot of finesse.