Yahoo appears to have put my site in a supplemental index

How else to explain huge difference between Google and Yahoo?

[diamondgrl]

I have a large site of 100,000 pages or so. All pages are reasonably optimized and unique and valuable information-filled contributions to the Web. Even though 50,000 pages are in Yahoo (and 90,000 in Google), I get 80 times as many referrals from Google as Yahoo.

It is easy to understand how a handful of pages might happen to rank very very differently in Google and Yahoo, but 100,000 pages?

The real answer appears to be that there is some sort of supplemental Yahoo index of pages like Google has and explicitly displays when there are few SERPs. I say this because my pages appear in very narrow phrase-match searches that return only a few pages in the Yahoo SERPs, but do NOT show up in broader searches when they should appear.

I had the same problem with Google until Googleguy heard about the problem and came to the rescue by tweaking something or another on the Google end.

So does anyone else have evidence this supplemental index exists and what can be done about getting put into the real index?