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You are dealing with two seperate animals here, the Yahoo directory is not Google and is the first set of results shown. A listing in the directory is essentially "fixed", you can't change it and adding doorway pages will not help.
If it's the site in your profile it looks to be a fairly recent addition to Y! [22nd Feb?], I would hold with the listing you have, you won't beat #1 or #2 but you should rank higher than you are now. I would give it a little more time before you take any further action.
Probably this should all be moved over to the Yahoo forum, but here goes anyway:
Yahoo is a directory. Directories put a LOT of significance on the use of keywords in URLs and most of all, in the site title. Plus, Yahoo now appears to be utilizing Google's PageRank technology as a ranking factor.
You cannot use a gateway site for Yahoo, since the editor who will review your submission will certainly catch it and reject it. The site submitted must be the actual site, the business name submitted must be the actual business name.
About the only way you have to impact on your Yahoo ranking -- without removing your site and rebuilding it under a different business name with a more useful URL (separated by hyphens) -- is to build Google PR. It appears that will boost your Yahoo directory positioning as well.
Good luck.