turbo chatter?

[s12pickup]

new to turbos.just piped in a front mounted intercooler.when i let of revs i get a shuddering sort of noise from turbo area.didnt get this before(or it was not as loud so i couldnt hear it)read about it on wikipedia and it says its either air gettin pushed back through turbo as you let off revs or the wastegate.which is it most likely to be and can it damage anything .thanks