Eva00 contained the trapped soul of Dr Akagi, which is why this Eva
repeatedly lashed out at Gendou, Ritsuko and Rei.
Eva01 contained the soul of Yui Ikari, and embraced Shinji hence his high
synch ratings, and could explain why Rei was never really able to synch with
Eva01, the soul and the body together again....
And somehow, after her suicide, Asukas mothers soul was trapped inside of
Eva02, and this explains Asukas low synch ratings when she becomes depressed
over her mother.