I've searched and found several threads on this, but no satisfactory answer.

My fully re-circed TXS RB34 (or whatever it's called) bypass valve has 6 washers in it, and whenever I let off the gas at medium to high boost, it sounds like air is blowing off like it should. (this is on a TXS FIMC, by the way).

If I let off the gas at low or no positive boost (but not full vacuum) it makes a Ch-ch-ch-ch-ch-ch..-ch..-ch....-ch sound that sounds very much as though it were coming from the passenger side of the engine compartment (from the turbo in other words).

Is the BOV opening and closing repeatedly at low boost making that sound(and by low boost I don't necessarily mean positive boost, just not full 10 psi vacuum), or is the BOV not opening at all and the slight pressure differential is stopping my compressor wheel and cusing it to spin backwards and making the funny sound?

Any ideas?

BOV isn't opening leading to compressure surge
try removing a washer...if you car stalls then put it back in and drive with boost! :)

do you have a boost gauge??? is the needle fluttering up and down at all???