Hi again guys. Got all of my coolant issues solved by looking at another possible issue.
It totally slipped my mind before, but would a car run hot if an engine slipped one tooth out of time?
I have a pretty wide duration cam (268 TT)...so the idle is never perfectly flat...in fact, it's actually kind of choppy with the larger injectors and head porting (and so on)...but would one tooth slipping out of time be enough to cause the car to overheat under a load (AKA acceleration) but allow for a more-or-less regular idle when stationary?
I don't know why I didn't think of it sooner, but after replacing every damned thing in the cooling system..it FINALLY crossed my mind that MAYBE it wasn't cooling at all!!!!