I've been a
SEO Specialist for 7 Years now and as of today, I've never heard heard yahoo is good in removing dead links from their index. We have provisions in google but yahoo is too very poor in the same. And I have experience in this case, where yahoo has not removed dead links for more than years of crawling. Are you sure about your statement and if yes, can you drop in any links where it says your statement is precise. I will get you links that exist in yahoo index though the pages are dead years together. Sigh!
Mc Mario