Adding header to Ajax request

Have you tried the headers config in the Ajax request:

Ext.Ajax.request({
    url: 'someURL',
    headers: {
        'accept-encoding': true
    }
});

You can specify request headers like this:

Ext.Ajax.request({
    url: 'yourUrl',
    headers: {
        'accept-encoding': 'true'
    }
})​