help troubleshooting a sound

[slo95]

the car is finally running great, although I HAVE to use a $5 bottle of Bordahls Knock Out with every gas tank (only that brand for some reason)...anyhow, now that i do not have pinging noises, i now can hear something else wierd. The only way I can describe it is years ago, i had a turbo dodge shadow. It made a sort of fluttering/whirrling turbo noise. NOW my car makes that similar noise? Vacuum leak? it is more high pitched than say a clunky/mettalic noise. Only makes it on wide open throttle, and if during the sound, I let off a bit and hit it again, it goes away. It is not gear whine either...definitely coming from engine bay.