We cleared this up via PM so I thought I would post it here so evryone could see in case they ever had the same problem:

A solution! Remove the (5) 7 millimeter screws that hold the base of the glovebox door to the instrument panel, then remove the glovebox door by squeezing the two sides together at the top which will allow you to completely take the glovebox door off.
Inside, at the bottom of the cavity you will see a gray plastic box measuring 6" long by 3 3/4" wide by 1 1/2" tall. It has (3) square heatsinks (metal fins) on the passenger side of the box and a blue connector on the driver's side. On the top of the box is either "Delphi" or "Delco" (couldn't make it out) "Electronics".
That gray box is the amplifier. So the amplifier actually sits under the glovebox
This is for Option Code "UQ3"

i believe your amp should be the black box inside your trunk. right in the middle
The amp mounted on the underside of the rear package shelf is the Bose system which came in the later model years (cletus has a '99 GTP) which was Option Code U85.