Basically, the moan has replaced the bypass valve's typical breath.
I replaced a rotted hose that went to that bulb with a sponge in it, and I thought the moan went away, but its back.

I checked th hoses and they seem fine. The only thing that i noticed is that the hose I used to replace the original is a bit softer.

Any ideas what the source of this prob is? Do these bypass valves go bad?

Gordie

 

They do but i would check all of your IC plumbing first. Especially, check the rubber coupling hoses and the flange nuts on the Y-pipe where they bolt up to the turbo compressor housings. The FSM shows you how to test the bypass valves in the event everything else checks out okay.