New noise on boost

[Justin]

Any body identify a kind of harsh fluttering noise on boost?
The performance is, I think, about the same, but it's bothering me.
It could be compared to a very severe pinking noise, but increases in velocity as the turbo winds up to full boost.
My suspicions are wastegate actuator oscillating - open and shut-, or, turbo rotor touching something (unlikely, I know).
It could also be described as sounding like a guiro (Latin American musical instrument that sounds like a noise you make in the side of your mouth).
Any ideas??
Regds,
Justin

[Justin]

Hmmm... boring... tracked it down eventually to the exhaust manifold gasket blowing and a cracked manifold - common on these 20VT engines.
Expensive transplant but extreme improvement in performance, now.