what is the best way to hook up a boost gauge, can you splice the hose that comes from the waste gate to the turbo?

This may help..:D
http://www.dieselplace.com/forum/showthread.php?t=91927

that is not the same year as mine. mine there is nothing there.

Yes, the waste gate line is the easiest. Another way is to use a Super diesel manifold. Or you can drill and tape into the intake manifold.

http://dieselplace.com/forum/attachment.php?attachmentid=609&d=1103251048

http://dieselplace.com/forum/attachment.php?attachmentid=2160&d=1108523402

Here, I did another Search for ya..plenty here for ya.
http://www.dieselplace.com/forum/search.php?searchid=2663686&pp=25&page=2

Just go through some of the post's for the lb7

I wasted a lot of time looking for that 1/4" rubber line that is part of the waste gate system on the older Duramax's. In the future I will throw away any diredtions that come with a product and come to the DP. Jasondt2001 has some great pics in his garage that detail every step of installing boost gauge. He has it detailed right down to hooking the lights into your dash