AJAX性能问题

We have developed a website using ASP.NET 4.0. AJAX functions work with no latency in intranet. But when it was moved to Internet, AJAX has become very slow. And the time it they take is inconstant as well.

So far I've done: I added following code to the ScriptManager

ScriptMode="Release" LoadScriptsBeforeUI="False"

And added following to the web.config

<system.web.extensions>
<scripting>
  <scriptResourceHandler enableCompression="true" enableCaching="true"/>
</scripting>

Still no luck.

The data getting transferred is only 82KBs, but it takes 4-7 seconds. Can anybody let us know what could be done to improve AJAX performance. Thanks in advance.