I think your issue may be because you are using the map function like you would if your data was in the json format. Below is an example using map with xml. You will probably need to do something similar.
function( xmlResponse ) {
response($( "Row", xmlResponse ).map(function() {
return { value: $( "ARBPL", this ).text() + ", " + $.trim( $( "KTEXT", this ).text()),
id: $( "ARBPL", this ).text(),
desc:$.trim( $( "KTEXT", this ).text())
};
}));