Disable the buffering in fastCGI on Linux server

I have a Linux server running a Debian OS. fastCGI is installed as well as php4. Previous we were using normal CGI php4. The php command 'flush()' that was outputting data during the php process ( normal CGI ) is now not outputting on fastCGI -- fastCGI is buffering all the data until the php process is completed, and then outputting to the browser. I need to know the exact setting / change to be made and in which file and where in the file to set the fastCGI to flush the output to the browser as it is receiving the flushed data from the php process ?