=========  /etc/nginx/sites/enabled/site.com ====================

server {
        listen   80;
        listen   443 ssl;
        root   /var/www/site;
        ssl_certificate /var/ssl/site.com.crt;
        ssl_certificate_key /var/ssl/site.com.key;

        server_name  site.com *.site.com;
        access_log  /var/log/nginx/site.access.log;
        location / {
            index  index.html index.htm index.php;
        }
        location ~ \.php$ {
            expires off;
            include /etc/nginx/fastcgi_params;
            fastcgi_pass 127.0.0.1:9000;
            fastcgi_index index.php;
            fastcgi_param SCRIPT_FILENAME /var/www/site$fastcgi_script_name;
            fastcgi_param moduleName MyVar;
         }
        location /admin/files/ {
            add_header Content-Type "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
            add_header LALALA "twststesets";
        }

}

=============================
URL запроса:   https://site.com/admin/files/Questions_Template.xlsx
Метод запроса:  GET
Код состояния:  HTTP/1.1 200 OK

=========== Query headers:
User-Agent:Mozilla/5.0 (Windows NT 6.1; rv:21.0) Gecko/20100101 Firefox/21.0
Referer:https://site.com/admin/?r=site/page&view=ReferenceTools
Host:site.com
Connection:keep-alive
Accept-Language:ru-RU,ru;q=0.8,en-US;q=0.5,en;q=0.3
Accept-Encoding:gzip, deflate
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

========== Response Headers:
Server:nginx/1.1.19
Last-Modified:Wed, 05 Jun 2013 15:18:24 GMT
LALALA:twststesets
Date:Thu, 13 Jun 2013 09:12:22 GMT
Content-Type:application/octet-stream
Content-Length:6333
Connection:keep-alive
Accept-Ranges:bytes