I see you facing a lot of problems with Rails 2.3.4 migration. It’s a very new release and probably you should wait for some more time to plugin authors to migrate.
I was browsing output_compression plugin code (http://craz8.com/svn/trunk/plugins/output_compression/lib/output_compression.rb) and it defines is_component_request? in AbstractRequest class. As far as I know, AbstractRequest was renamed to Request in Rails 2.3. Although, it is not a good idea to monkey patch the plugin, but if it’s very urgent you can try renaming AbstractRequest to Request and see whether it solves (or create new) problem.