Below is the information regarding an AMP upgrade from a Boxster with a M490 Option AMP (4x40 W) to a 996 Coupe - 6 Channel AMP (996.645.311.00 - 6x40 W).
My wire AMP apdapter was long and puts the female receptacle that accepts the brown plug just above the gas pedal. The OEM apdapters are very short and installation would be slightly different. I have pictures of that installation as well if any one is interested. I removed the front trunk carpet and battery to gain full access.
The cable comes out and into the trunk thru the rubber plug that is also used by the CD changer. You can see the cable can be attached quite nicely to existing wiring as noted above.
I also was installing a CR3 CD changer at the same time. I tied all wires to existing wire bundles and ran past battery tray and into the plug above gas pedal on drivers side.
When penetrating the rubber plugs, I cut small x's with an exacto knife at the top end of each plug. When finished I used clear silicone caulking to keep water tight integrity.
Below is the inside of firewall above gas pedal. You can just see the end of the female adapter that accepts the brown plug on the right side of photo. That adapter is the end of Harvey's cable. Having someone helping when you penetrate the firewall keeps the rubber plug intact. I actually pulled the wire from inside to the outside by running a stiff wire thru the rubber plug from the battery side and taped it to the cable and pulled it back thru.
At the AMP pictured below, Left Rear Positive+ (Red wire) is attached to #6 pin and it's Left Rear Negaitive-(Black wire) to #16 pin.
Rear Right Positive+ (Green wire) is attached to #5 pin and it's Right Rear Negative- (Black wire) to #15 pin.
In the picture below, PINS 6,16,5 and !5 are easy to find on the AMP. The circle indicates the guide or key that needs to be removed for the harness to mate up. I used a sharp wood chisel to shave it off.
Finished installation of CD Changer and AMP below:
