People always ask if the diaphram, for routing your fuel lines, (on the how to page) is correct. I myself have had problems with it.  Can anyone help clear this up?

this info is correct: http://www.gstwin.com/fuel_hose_routing.htm

even if this is the correct way, I put a in-line filter in the line that goes to the carbs, it will fill up on prime and the bike fires up but after a mile of riding the gas is all gone.  When its in the (on) position nothing, on reserve I can see air pushing the fuel in the filter. the only other thing I can think of is a hole in the vaccum or somewhere. All the lines are new though???
What do you think?

Start at step 4 in this old post, but perform each step with the ON hose rather than the RES hose.

Both the ON and RES fuel switch positions use the same vacuum to allow fuel through ... but the fuel is delivered by different hoses.

As stated in the linked post, you could have a blockage in the fuel selector switch, or the ON hose itself, or the in-tank petcock.

OR ... there's enough fuel in the tank to cover the RES drainage level, but not enough to cover the ON drainage level. 

Thanks, I definatlly appreciate the post!!

What kind of in-line filter did you use?  If you used an automobile filter, it can cause fuel starvation problems.  Most cellulose car filters filter well, but are designed for pressurized systems with fuel pumps.  A gravity-fed system as in the GS just won't push enough fuel through one.