Well it looks like they won't let me attach a wave file so I'll try to describe it.
A fraction of a second before I start the engine and for a second after I shut it off (only when still cold) there is a fast knocking sound from behind the dash/firewall. Its comming from the area of the lift pump I think but I can't find it. Whatever this noise is, the truck always made the sound when I just shut it off after running only for a few seconds. After changing my cold start advace switch it now makes the noise quite loudly for about 5 minutes before going away. I'm not too concerned but new noises do make me a bet nervous.
