If you were near one of our two shops I would of invited you in for a listen.
I am not sure what your wistle is, but I can tell you how to ensure the bypass valve is working correctly.
With the engine off, look at the bypass valve. It should be in the closed/boost position. Work it with your hand and make sure it is all the way closed against the stop. If the actuator is not installed properly, well at least on the 1st gen, the actuator rod can drag on the housing and prevent full closer. Force it open against the spring and let it go. It should quickly snap shut.
Now start the engine. The bypass valve will move all the way to the other side into the bypass posistion. Now reach over and quickly snap the throttle plate full open an quickly let it go. You should see the bypass valve quickly close and then when you release the throttle it should quickly move back to the bypass posistion.
If all that works correctly, you may need to look somewhere else for the noise.
Gadget
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