I just compiled an old application from Delphi 2010 to XE7.

I just compiled an old application from Delphi 2010 to XE7. The main purpose of the software is processing toons of XML files. We had to run the old D2010 version because of performance! The XE7 is much more slower when processing the same data.
We are using TXMLDocument to load the files. Any clue about optimization?