On MOSS 2007, there are 2 lists, projects and issues. Issues list has
a lookup field back to projects with project title shown in issues list.

When try to create a filtered view of issues based on project using
OOTB querystring filter, it can only filter by project title because
that project title displays in issues list. But I would like to filter
by project id.

How can I achieve filter by project id?

I know I can display project id instead project title in issues list,
but this would not be user friendly. Another option is to have 2
lookups fields back to project on issues, however, this introduces the
problem of synching the project title and project id in issue list.