Bongo Fury

Did you test the old & new stat's against each other in a pan, just cos it looks ok doesn't mean it was opening at the right point or opening enough at the top end, main thing is you've sorted it I think the rad weeps were a large part of the problem too as its supposed to be a pressurised system & was probably sucking air back in on cooling.
Remote diagnosis is not an exact thing, difficult to know exactly what's happening & why when it's not happening in front of you.