I have a 99 Mustang and recently replaced the mach 460 system (two seperate units) with an aftermarket unit. It works fine except for there is no sound. My aftermarket system did not have a place to hook the amp turn-on or amp ground so I left it and I assume that this is the reason for my problem. I would like to keep using the stock amp to power my speakers so I am wondering where or how I can hook those two wires. I think that I might be able to hook the amp turn-on while to the ignition switch wire coming off of the head unit. This could be a problem if the amp is not regulated for 12 volts. Does anyone have any advice that will help me? Also, where are the amps located? I would appreciate any help you can give me.