Most containers regards the TRACE method as a security risk and have it disabled by default. If it isn't working you'll have to enable TRACE in your own container. If you are running tomcat add allowTrace=true to your Connector in server.xml. Check their documentation of the HTTP Connector for more information.
The RFC states in section 14.38 Server that "If the response is being forwarded through a proxy, the proxy application MUST NOT modify the Server response-header."
However, it isn't possible to have tomcat not add a Server header of it's own, this is a problem with tomcat not with J2EP.