I've tried using xmlData.Header.toString().replace(/&lt;em&gt;/ig, '<em>') to convert the html entities back to characters so the web app will render the header correctly, but the header continue to render as <em>#########</em>. It seems like the replace is bypassing the < and >. Or it's being converted back.
I have tried to replace just the "<" and ">" to "<" and ">" without any success. But I was able to replace other letters, outside of the tags, e.g., changing the letter "a" to "A", Barcelona to BArcelonA.