You did not mention if you are hearing the noise from outside the car or from the interior.

I am doing a complete sound/waterproofing right now on my Chally.

Here are a few tip....
Look at all the bolts, nuts, grommets, plugs etc on your firewall. Make sure they are all sealed.
A small hole can make a big whistle.

Check your interior vents to see if they are sealed tight.

I have my carpet out at the moment, so I do the easy way....with my garden hose !
I spray the entrire firewall, then look at my floor boards for any leaks. Follow the water line to find a hole.
I also use a shop light on the engine side of firewall, and can see any holes under the dash from the inside.
You can check for vent leaks by spraying some water thru the cowl vents.

I do my doors and windows the same way, as well as re-direct water channels where I can.