ループで作った複数投稿ID配列を使って複数投稿をquery_postsで取得する

PHP

//IDをループ
foreach($cats_list as $item){
  $ids[] = $item['post_id'];
}

$args = array(
  'posts_per_page' => -1,
  'post__in' => $ids
);
query_posts($args);

手書きで配列を作る場合

$args = array(
  'posts_per_page' => -1,
  'post__in' => array(101,102,103),
  'orderby' => 'post_in'//配列がはいってる順に表示
);
query_posts($args);

参考:How to make WP_Query 'post__in' accept an array?