Drupal chat slowdown my application
AJAX chats are pretty resource hungry by nature when running on Apache, so there are no easy configuration switches that will instantly give you better performance, I'm afraid.

The big difference between chat implementations is that GMail and Facebook uses a different backend, more suitable for AJAX polling / push. The node.js backend for Drupalchat might be able to help you in that regard. If I were writing my own chat from scratch, I'd probably try out http://www.ape-project.org/ which seems to be pretty good featurewise.