Uncap headers on a camaro ?

i have a 96 z28 with a LT1 corvette engine right now i don't know what kind of exhaust i have on the car but is sounds good and is some what loud i think it might be flow masters i bought gl packs but have not put them on because i heard that there is a kit you can buy the puts a lever in your car that you can pull and it will uncap the headers and if you push the leaver back in it will recap them does anyone know what this kit would be called