How to change IIS8.5 Content-type?

Hi,

I am started the management of a Win2012 server. PHP+MySQL is running with IIS85.

There are many sites with Latin 1 encoding, but the server sends out Content-Type:text/html; charset=UTF-8 header.

I'd like to change it, but for separate sites I can only append additional charset-s, not replacing the global setting.

Where can I find the global setting or how can I override it for specific sites?

Thanks for your help,

tamás