I don’t know that you’d notice a difference without it but I like to think the factory put things like that for a reason. You can buy a new one from Detroit muscle technologies.
My 91's is long gone and I have no ill effects. It would be nice to have all of them in good shape to help keep water or mud out of the engine if romping it hard or in heavy weather.
They have a few handy things. Tail light screws and gaskets (quality black screws), fender splash shields, gas tank mat, and some other stuff. I wish they would make new rear wheel well liners. All of them are cracked by now but I really like to have those. I hate the exposed tub back there. Makes the road so much louder.