quick carb question

[Ry_Guy]

Hi, I'm new to the site and like what I see.  
Got a 96 gs that stalls out when I pull the clutch in and let off the throttle. The carbs were cleaned 3000 miles ago and I did a float height check (thanks Kerry) that passed.
Seems to be a deprivation of fuel, so I suspect a faulty petcock vacuum hose or fuel petcock itself.
My questions: are my suspicions accurate? and what's a good place to order replacement parts? or is it something I can fix?  :dunno:

[Kerry]

You didn't mention how creative you've gotten with the idle adjustment screw:



Also, if the engine is still cold you need to give it some choke.

Do you have any more details?

[Ry_Guy]

Occasionally it doesn't stall when I slow to a stop. When that last happened, I adjusted it right there to 1200 rpms.
It will stall any time, warm or cold. Also I noticed an air bubble in the fuel filter that likes to stay there (I tried reinstalling it). Choke has little effect. -When I pull it in all the way, the engine also kills, warm or cold.
One more detail I hate to acknowledge: occasional whistle noise near the cylinder head or carb, can't quite tell, but it pulses with the engine's noise.