Attempt to improve WP search, can someone check my SQL query?

I’m stumped. I’ve done a bunch of work to filter what posts get pulled in a WP search and then even more work sorting those after they’re pulled from the DB. My main problem now is getting results matched by Tag. I’ve just been running the straight SQL query and checking the output rather than running it through WP over and over.

First the search query as WP generates it (my filters added and I’ve expanded out the important part):

SELECT SQL_CALC_FOUND_ROWS  
wp_3_posts.ID FROM wp_3_posts  
LEFT JOIN wp_3_term_relationships AS trel ON (wp_3_posts.ID = trel.object_id)
LEFT JOIN wp_3_term_taxonomy AS ttax ON (  ( ttax.taxonomy = 'post_tag' )  
AND trel.term_taxonomy_id = ttax.term_taxonomy_id) 
LEFT JOIN wp_3_terms AS tter ON (ttax.term_id = tter.term_id)  
WHERE 1=1  
AND 
(
 (
  (
   (
    (wp_3_posts.post_title LIKE '%neck%') 
    OR
    (wp_3_posts.post_content LIKE '%neck%')
   ) 
   AND 
   (
    (wp_3_posts.post_title LIKE '%pain%') 
    OR
    (wp_3_posts.post_content LIKE '%pain%')
   )
  ) 
  OR 
  (
   (
    (tter.name LIKE '%neck%')
    AND
    (tter.name LIKE '%pain%')
   )
   OR
    (tter.name LIKE '%neck pain%')
  )  
  OR 
  (
   (
    (wp_3_posts.post_excerpt LIKE '%neck%') 
    AND
    (wp_3_posts.post_excerpt LIKE '%pain%')
   ) 
   OR
   (wp_3_posts.post_excerpt LIKE '%neck pain%')
  ) 
 )
)  
AND (wp_3_posts.post_password = '')  
AND wp_3_posts.post_type IN ('post', 'page', 'attachment', 'syndicated') 
AND (wp_3_posts.post_status = 'publish')  
ORDER BY wp_3_posts.post_date DESC LIMIT 0, 7

The first part which grabs the necessary tables with joins seems to be just fine. The search I’m running is for “neck pain” and any posts with those words in the title, content, or excerpt show up as expected. I have one post tagged “neck”, “pain”, and “neck pain”. That post ID does not return with this query. What driving me nuts is that if I remove the part of this query that looks into the post_content and post_title, my tagged post does show up. Specifically, if I remove this:

(((wp_3_posts.post_title LIKE '%neck%') 
OR (wp_3_posts.post_content LIKE '%neck%')) 
AND ((wp_3_posts.post_title LIKE '%pain%') 
OR (wp_3_posts.post_content LIKE '%pain%'))) 
OR 

which leaves my query as

SELECT SQL_CALC_FOUND_ROWS  
wp_3_posts.ID FROM wp_3_posts  
LEFT JOIN wp_3_term_relationships AS trel ON (wp_3_posts.ID = trel.object_id)
LEFT JOIN wp_3_term_taxonomy AS ttax ON (  ( ttax.taxonomy = 'post_tag' )  
AND trel.term_taxonomy_id = ttax.term_taxonomy_id) 
LEFT JOIN wp_3_terms AS tter ON (ttax.term_id = tter.term_id)  
WHERE 1=1  
AND 
(
 ( 
  (
   (
    (tter.name LIKE '%neck%')
    AND
    (tter.name LIKE '%pain%')
   )
   OR
    (tter.name LIKE '%neck pain%')
  )  
  OR 
  (
   (
    (wp_3_posts.post_excerpt LIKE '%neck%') 
    AND
    (wp_3_posts.post_excerpt LIKE '%pain%')
   ) 
   OR
   (wp_3_posts.post_excerpt LIKE '%neck pain%')
  ) 
 )
)  
AND (wp_3_posts.post_password = '')  
AND wp_3_posts.post_type IN ('post', 'page', 'attachment', 'syndicated') 
AND (wp_3_posts.post_status = 'publish')  
ORDER BY wp_3_posts.post_date DESC LIMIT 0, 7

Maybe there’s something I’m not understanding about SQL here, I’m a bit of a hack at it. Any wisdom would be much appreciated, thanks!