Cold Air Intake Noise

It's my understanding that the whistling noise is usually caused by a non-perfect fitting where the filter meets the intake. You can try wrapping around it with a decent tape to see if that fixes the problem.

As for a sucking sound when you stomp on it, if you just think for a second of how the engine works, then you'll realize that's a normal sound. You open the throttle, which causes a vacuum and the air starts sucking in, however the RPM of the engine doesn't immediately skyrocket because there's a delay between starting to suck at the intake end and actually being able to use the air for combustion in the cylinders. You may also notice a different sound when you go from high throttle and let it idle down to normal throttle, because there's a vacuum in the whole pipe, but when you close the throttle the air has nowhere to go, similar to what causes turbos to require blow-off valves (but turbos deal with much higher pressures/vacuums).

b