Your original concern was that with the AST removed the water pump would overwhelm the spring cap at high rpm. I agree, the issue is next to impossible to diagnose...because it does not happen. That’s not circumstantial evidence. That’s closer to direct evidence, gathered longitudinally by many owners, over many cars, many miles, many years and varied conditions.

 

I eliminated the AST on my car without consequence. I used the Banzai billet cap for the thermostat housing. My engine did not have the correct thermostat housing so I picked up one from a Club Member and as an added bonus, when I removed the old housing I found the thermostat installed backwards! Engine was rebuilt by a previous owner, only had a few thousand miles on it but I was amazed that the engine survived that experience.
After you fill and bleed the engine you should check after the engine has been run and cooled down. I checked it every morning for a week, each day I added a little more coolant, it bled the air out after a few days and has been running great .
Dave