Bloodworms? I must ask . . .
If you're attached to the tang, keep it. Just be sure it has enough swimming room and keep an eye on aggression levels. Keep in mind that you may see more attitude when you add something new.
As Small Alien says, there are a lot of great fish you can keep in a 90. I haven't braved a leopard wrasse yet, but there are lots of other wrasses you can keep assuming you've got a cover on your tank. They add a lot of activity and are much easier to keep than anthias, which are beautiful but a pain (IMO). I think Bartlett's get as big as lyretails and they're kind of obnoxious. Sunburst anthias get a decent size, but are very passive - maybe too passive in a tank with an established yellow tang.
Some wrasses are also kind of obnoxious, so find what you like and ask. Lots of people on here with great knowledge about them.