Get used to that, you CANNOT slam the CRS carbs open at low RPMs without you bogging down, remember these carbs don't have an accelerator circuit. My carbs are tuned pretty darned close, and I still can't slam 'em, you have to roll into the throttle. About the only thing you can do to help a bit, is richen up your needle setting, but even that won't entirely fix it. My best guess without constantly studying the tach, is anytime under 1/4 throttle below 4000 RPM, and they'll bog. Don't know anything about the whistling sound, but then again, my pipes are darned loud. For whatever it's worth, here are the jet settings that I'm using right now, this is with Freak, Cams, and Pipes:
Slow: 55
Air Screws: roughly 1-1/4 turns out
Needles: 5183, 3rd Notch Down
Main Fuel: 115
Main Air: 230 (I think)
Another thing to consider also, if your carbs aren't synchronized closely enough, it won't have helped the bogging any, and you'll have very rough throttle response at low throttle openings. Hope this helps.
