i considered cavitation, but one weekend i decided to shift at 5k rpm (usually do around 6k) and it still had the problem. pretty damn sure there is no air in the system, ive opened the cap and refilled quite a few times and also done the squeezing the pipes thing.

thermostat has 6 small holes drilled in it to let fluid by in case it is stuck, but not so much that it flows too quickly.

update from today is that i saw the temps go up a little while sitting in traffic... i was sitting outside a restaurant with the car on and i smelled a little burnt coolant. also when i got back popped the hood and saw the fluid level in the tank (the main one, not the reservoir by the turbo) has risen quite a bit since this weekend with no added fluids.