Ok my hatch had a b18 swap in it when i got it, and below half throttle it will whistle really loud. i thought it was maybe a throttle body gasket problem but it looked ok, then i noticed the bore was 62mm and had "HAD" stamped on it, is that 62mm larger than a stock b18 throttle body? i figured if its sucking in more than stock air flow the whistle could be from just the throttle body's butter fly opening

 

if its not the throttle body what else could it be? it does it whether im running an intake or just open TB

 

Mine whistles all the time, it is just vaccuum causeing it. The silencer on your stock intake takes care of the whistling, if you have any kind of intake it will be less restrictive causeing more noise, you get used to it.

 

do you have an aftermarket intake on the car

some of them out ther whistle a partial throttle sound to be your problem
the whistling is probally something loose and vibrating at such a high speed it whistles kinda like a bomb dropping

 

thanks

 

There's like 20 different theories on why it whistles. Not sure which fits you

Oh and I think you have a Type R throttle body there.

 

Son of a bitch thats gotta be why mine whistles. I've got the stock intake (that lames *** Y7 DX one) and i removed the resonator a while ago. I started noticing whistling and i've been assuming it was the TB gasket. Guess not. Still haven't gotten used to it though and its been almost a year haha