Flaky? Hm. I can relate to that. Somehow.
I've recently built a new system quite like yours: Asus P8P67 LE, 8 GB, GTX 580.
I haven't touched that TPU switch.
But, my system would boot very very slowly, the Bios part of it. Started happening after I had connected my USB devices.
And, once in Bios, the cursor/pointer/menu selector went scrolling continuously, as if the down error was pressed constantly, or the mouse was moved downwards.
Turned out it was one of my game controller devices, one that used to be a game pad, but of that I now only use its electronics for some 12 buttons.
No switches/pots are connected to the X/Y/Z axis of the controller. And that is something this Bios cannot handle. It recognizes it as some kind of USB controller and accepts its constant inputs...
Old bios never did that, but that one was much older, and did not have mouse control.
I've solved it by only connecting that specific controller whenever I do need it. And have it disconnected at boot.
Am already working on a Bodnar-board to replace that weird gamepad thing...
They still manage to make stuff more 'intelligent' and thus more complex.
More of a challenge for us to troubleshoot issues...