factory amp 95 f 150?

Have a 95 f150 in the shop and the customer had tried to install a HU on his own and cut out the premium plug(harness in a gray sheath) the colors i get for the wiring are completely different then everything i'm finding so i just tested the wires with a tone generator. key off and on i get nothing. Does this truck have a factory amp? where? if not, what am i doing wrong? Thanks in advance guys. Brent

Just to clarify since my grammar was pretty terrible, the wiring colors on the wiring diagram i have(off of the vehicle wiring diagrams on this site)don't match the colors i have in the truck. I have stripped back all of the speaker wires and used my tone generator on all of them and i get no noise. So my thoughts are that some time in the past someone cut the wires that connect to the speakers, or there is a factory amp that isnt turning on. Give me some ideas guys. Don't care if they might not be the answer, just need something to try.

i just googled 95 f150 amplifier location and the first topic that came up someone gives good info on how to get at that amp.  He said it is above the accelerator pedal on the knee panel if that makes sense.  To remove it, bend tab on the plastic plate & allow the amp to slide down & out. Then unplug the 2 big connectors in the harness. Remove the radio & unplug the 3 connectors, and feed the amp wiring out of the dash.  this is copied from steve83 from fordf150.net give him creditAdvanced

Thats crazy i googled it like 10 times and didnt find anything very helpful. Not sure what the problem ended up being but i'll let you guys know what i did. The factory harness 12v constant wasnt working so i ran a new one fused from the battery. Got the radio to work properly, but no volume from the speakers. Decided to try and provided 12v constant to the factory harness and when i tested the speaker leads again i could get the back two speakers to work. Even if i were to just touch one of the rear speaker wires with my fingers i would hear a high pitched humming. Couldnt get the front speakers working so i just ran wire from the HU straight into the doors. not the way i would have liked to do it, but it worked. Wondering if the person who worked on it before i did had burnt out two channels on the factory amp.