I was reading this: http://maypalo.com/2012/01/01/tutori...ne-43gs-guide/ and http://www.ijailbreak.com/cydia/setu...ver-for-spire/ Not sure how far you are in the process, but these should help you out.
Hmm...take a look at this one. http://www.theiosexploit.com/2011/12/how-to-grab-iphone-4s-siri-authentication-keys/
Check out this guide for the SiriProxy. Seems a little more in-depth. http://www.iphoneroots.com/2011/11/howto-create-siriproxy-server-unlimited.html