The problem is that there is no `refine search` function in the search engine, so you have to get the relevant results in one shot.
What you can do to decrease the number of irrelevant threads is:
1- Restrict the search to the 911 technical forum
2- Restrict the search to titles only.
3- Use and to have all the terms you want
In your example, `oil filter cool cap` in titles return nothing, but oil filter returns 37 threads, which is better than 169.
Now, `oil and filter and cool and cap` in threads returns 9 threads, which is probably as good as it gets...
http://forums.pelicanparts.com/search.php?action=showresults&searchid=628536&sortby=lastpost&sortorder=descending
Aurel