I'll keep on eye on the dipstick. I checked it a couple of times within the last few days and it may have moved up a millimeter if at all. I'm just not sure what the next step would be - I was hoping there was an item that I overlooked that was causing a blockage. Thanks! Meanwhile just drive with ...

That's been my hunch as well with that spendy upper pipe. The bottle-neck is where the PTC nipple ports into it & that's the most likely & most obvious (as well as easiest to check) place for a blockage, thus why I've never replaced one. I figure if you're cooling ok (coolant temp), there ar...