As you've discovered, once the GSA learns about a URL it doesn't need
to rediscover it by following a link to it. Recrawling specific
collections isn't going to force the GSA to forget those URLs if
they're still valid.
You can reset the index, which will force the GSA to forget everything
it knew about your content and start from scratch. This would affect
the entire index, and is obviously a drastic measure.
You can enter URLs in the Do Not Crawl Patterns box. If there are no
longer links to those URLs, you should be able to remove them once
they've been dropped from the index.
You can use the delete action within a feed to tell the GSA to delete
documents from the index.
Dave Watts, CTO, Fig Leaf Software
1-202-527-9569
http://www.figleaf.com/
http://training.figleaf.com/
Fig Leaf Software is a Service-Disabled Veteran-Owned Small Business
(SDVOSB) on GSA Schedule, and provides the highest caliber vendor-
authorized instruction at our training centers, online, or onsite.