Opinions?
 

I am planning to do a coolant system flush in the next week or two and was wondering, should I proactively replace infamous plactic parts #9 & #1?

Seriously, I have no idea, but if you have to ask....

It definitely wouldn't hurt to swap them out. They are pretty cheap too. It would be best to refresh the whole cooling system and know that everything is good but if you don't have a whole lot of cash to spend and the coolant is coming out anyway...why not?