What are these little rubber o rings for?? The ones circled in red. Never noticed or realized what they are for and have always been paranoid I've left out something crucial on accident.

 

I think those are for the smallest seal that goes onto the fuel injectors for 22R-E engines.

Look at the top arrow in the second photo in this post: https://www.yotatech.com/forums/f116.../#post51073383

If not, I am tired and need to look at the picture again in the morning......

 

Thermostat o-ring,
heater pipe to intake manifold,
4 injector o-rings.

 

Bingo!

Some kits don't have the heater pipe to intake manifold o-ring. The last Beck-Arnley kit I used did not have one.