Hi,
It won't hurt to raise it a little bit.
There are a few more signs of an RI though than just the whistling - if the snake is in shed or has a retained shed over its nostrils it can cause the noise when it breathes.
Are there any signs of excess mucus in the snakes mouth - any drooling or signs of it in the waterbowl or smeared on the cage furniture?
Do you see the snake spending a lot of time with its head raised and its mouth open?
dr del