Wher would I find the right sound insulator in a 1990 Buick lesabre

I have a 1992 Oldsmobile 88 and the main fuse box cover below the steering wheel also states "for access to additional fuses remove right sound insulator". I found that this is referring to a long black plastic bar just under the dash. It runs from about the center of the car all the way to the passenger side. Remove the 4 screws that hold that on and you'll see the second fuse block off the the far right of the passenger side up under the dash. Hope this helps and is the same for other similar cars mage by GM around the early nineties.