There is a difference, actually.
"EVEN THOUGH" is used to express the idea that, in spite of an EXISTING situation or something that happened in the PAST, another thing IS still true. For instance:
"EVEN THOUGH I found out she's got a boy friend, I still love her".
"EVEN IF" is used to express the idea that something WILL still be true IF something else happens (that is, in the FUTURE). For instance:
"EVEN IF she leaves me, I will always love her".
In both cases, "EVEN" is used to emphasize the situations.