Cyclone, you will always enjoy lots of competition – Yahoo will always show ~1000 results, and all of us want to be at the top spot :Nod:
Plus, nothing lasts forever, and soon somebody will move you from the top, then the top 10, etc.
The only way you could “get your site back” is to contact Yahoo for review and possible re-inclusion.
You could get the same domain name back in a little while by adding content, changing hosting/IPs, completely re-designing, but all this is just as painfull as building a new website…
If you have just 2-3 websites, you will have to choose your search engine, because it’s almost impossible to rank top on all of them at the same time.
Yahoo is the easiest if you would like fast but temporary results, due to the large amount of spam it accepts. (Although with the recent Google update, the spam thing is true as well.)
The lack of sandbox with Yahoo is great, but do not expect to spend too much time enjoying a great ranking, for that same reason.
Anyhow, if your sites rank good on Google – just “work them” for Google, and start a new website just for Yahoo.