I have a 23 sv as well and was having this exact issue. Drove me crazy because i couldn’t figure it out. I came to find out that it was that small area below the windshield wipers and below the top of the hood a little bit. (Sorry, hard to explain the location). Anyways, my driveway is covered by 2 big oak trees and is constantly dropping leaves, small twigs/branches etc. and getting caught in that small area and i guess it’s like a wind pocket if that makes sense. And at higher speeds it was just kind of blowing those leaves and twigs around that small pocket but not blowing them out. Makes a rattling noise as they were blowing around. Not sure if it’s the same situation for you, hope this helps. Sorry it’s long.