I don't believe VNC has the capability of transferring audio.
I am have got my iphone connected to my carpc through vnc but i was wondering if there is any way to to sent the iphones audio to the carpc through the vnc connection, this would allow me to use the phone through the cars speakers
I don't think you can send the Iphone's audio wirelessly to a computer (easily). But I believe if itunes is on the PC, you can use the iphone as a remote control for it. If your itunes library is the same as the iphones, that would probably just as well.
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VNC as a protocol doesn't have support for audio