I can hear a clicking noise coming from the general area of the turbo pack/intake hoses. It's kind of like a ratcheting noise. It isn't there when the throttle is open any amount. It only appears when I come off the throttle and the car is slowing down. Dont hear it when the car is sitting idling.

Does anyone know what it could be?

I am guessing that it is in some way related to my boost problems. i.e no secondary

 

Open hood, twist throttle manually and try to duplicate.