All files from this thread

File Name	File Size		Posted by	Date
nginx.conf	2.7 KB	open | download	B.R.	10/07/2013	Read message
test.php	77 bytes	open | download	B.R.	10/07/2013	Read message
php.ini	67.3 KB	open | download	B.R.	10/07/2013	Read message
nginx_php_backend.pcapng	5.5 KB	open | download	B.R.	10/07/2013	Read message

Have you seen this one;
http://stackoverflow.com/questions/8882383/how-to-disable-output-buffering-in-php

Also try php NTS, it might also be that a flush only works with non-fcgi.