One of the local dealers stocked up on em and had several in stock when I went in...so I bought one. They mentioned something about a "plug" that will go in it that they're getting in soon.....I didn't really catch what it was for. Anybody know what this "plug" might be?

Probably to plug up the hole left behind by your decomp assembly if you are to remove the assembly and the cable, etc. That piece only costs a few dollars...