I've never trusted translations much, so when I saw the various versions of the "dirtiest verse in the Bible" by the different biblical translators, I decided to check out Ezekiel 23:19-20 myself. Here's my crack:
19: And she added to her prostitution/promiscuity so she to recall the days of her adolescence, when she prostituted/slept around in the land of Egypt.
20: And she lusted after their libertines, of whom like the meat/flesh/penises of donkeys are their meat/flesh/penises, and the emission of horses their emissions.
You see, any translation of the Bible makes a lot of assumptions based on context etc. And ancient Hebrew just didn't have that many words, compared to modern English. So often, a word can have any number of similar meanings.
Notes on the above translation:
prostitution/promiscuity - The word, biblically, "Zon'oot", for prostitution is also used for general sluttiness. So it's ambiguous, but I think the sense here is promiscuity rather than money for sex.
adolescence - a biblical term for a time when someone is no longer a child but not yet an adult, twelve or older for a girl. But I suppose there's no need to get too technical, and youth would do too.
libertines -- seems to be the same word as used for concubine. I think the idea is of people who live for sex, similar to the modern use of the word libertine, or perhaps nymphomaniac.
meat/flesh/penises - the word is Bassar, meaning flesh (as in "all flesh is grass", Isaiah 40). It also means meat in modern Hebrew. From meat/flesh it isn't that hard to get the idea. I don't think (but I might be wrong) that there is another biblical word for penis. So the old translations aren't wrong as such, just misleading.
emissions - pretty much the same story. The word has the sense of issuing, emitting. And we can get the hint.
And the moral of the story? Sometimes both -- or all -- translations can be right.