I recently bought an '04 SVTF, that the PO had installed a short ram intake on, it whistles like crazy. I have found through light application of the gas while driving ( I have a sensitive foot and can keep it at one spot for a while, a result not having cruise control for 8+ years.) I can get the throttle open to just enough where that's all I hear is a light, consistent whistle.
I can tell you from experience that on my AEM CAI from my original SVT, you could also hear a slight whistle at partial throttle, but it was more prevalent if you floored it in say 4th around 30mph. You could really here the intake suckin hard.
I'm pretty sure the whistle you are hearing is a normal side effect of having the SRI on your car. Shouldn't be alarmed about it unless you start hearing abnormal whistling.
I am an outspoken and enthusiastic Christian. I enjoy evangelizing to people with the help of anointed hip hop & rock. I think there's something truly AWESOME about listening to good music that truly makes you feel good inside.