What, over the air sync, or are you trying to do USB cable sync?
The reason I ask is because on a jailbroken iPhone at work (where wifi is verboten), I have taken to using iProxy and reverse ssh, and then just tell my iPhone to sync to 127.0.0.1. Performance is excellent.
ssh -p 2222 -R 5000:my.machine.ip.address:5000 -g root@localhost
Where my.machine.ip.address is the actual LAN address that you see pop up in TR for iPhone sync. Then I just use ssh key sharing for root user (you could do it for mobile user too, doesn't matter), and off you go.
Of course if you're trying to use native usb then I don't know what to tell you. :D