[wp-hackers] the right hook for custom content

[Malaiac]

I'm looking for the right place to hook for pages like
www.site.com?custom_content_id=3
add_action('parse_query') does not work when there is nothing in the query

adding  'custom_content' as a query var ( fill_query_vars) could be
good, but there is no action between fill_query_vars and the main
parse_query process
a manual $wp_query->fill_query_vars(array('custom_content','custom_content_id'))
on init does not work either.

Malaiac

(the next question will be :
and what if I want to have rewrited custom content like
www.site.com/custom_content_3.htm  ?
I've already added some custom permastructs & custom rewrite tags)