With the help of Ed I was able to show different headers in different forums without adding more styles. :)

Very simple, you don't even have to edit any file.

In phpinculde templates:

add

if ($getforum[forumid] == X )
{
$header = implode('', file("header_1.txt"));
}else
{
$header = implode('', file("header_2.txt"));

}


Where X is the forum number. And header_.txt is the files where the header code is.

Enjoy.