https://www.justanswer.com/uploads/VirtualWrench/2009-05-06_184951_pioneer.pdf I have reviewed the above wiring diagram and the harness documentation for a Metra 70-1771 and a lot of things do not make much sense. tjtheman007 also did a good write-up in this thread and I looked that over too. I have not taken delivery of the 2004 Sport Trac yet but I know it has the Pioneer 6 disc changer and an amp behind the rear seat. Unlike tjtheman007, I sure mine does NOT have MP3 player on it so I don't know if this qualifies as the Adrenaline version. Its just a 6 disc changer and pretty basic looking, ford styling front plate. Crutchfield tech support indicates that the Metra 70-1771 install strategy ignores the OEM sub-woofer and sub-woofer amp which seems lame and just run front speaker wires to the new head-unit. I should be able to tie into it like tjtheman007 did with the RCA line-level jacks. Questions - What is going on in this wiring diagram with the front left and right speakers? It shows one pair driven by the head unit and another pair driven by the subwoofer amp and they are all the same colored wires. Both Fredness and tjtheman007 appeared to only use line-level outputs from the new head unit and the factory OEM subwoofer amp to drive the front speakers. That makes perfect sense to me but why did Ford do it differently? Crutchfield strategy also makes sense as the Kenwood DPX502BT HU is probably a better amp than factory. The link to the Metra 70-1771 has a couple undocumented wires. The black/orange is undocumented and crutchfield tech-support indicated that it was no longer included with the unit as it was un-used. The black with white stripe is also undocumented in the wire chart and Crutchfield tech-support indicates its for an amp ground. The PDF wiring diagram shows a pair of undocumented wires between the head unit and the amp. On the head unit they are PIN 1 RED/BLK (-) and PIN 2 BRN/ORG (+) . On the amp the same colors plug to PIN 1 - and PIN 8+. Is PIN 8 BRN/ORG where the +5V signal is supposed to go? Crutchfield did not include the 12V/5V converter in the recommended hardware although they do sell it for $20 as they bypass the amp altogether. Or is 1 & 8 a line-level subwoofer signal? This thread for a '98 suggest as much although the polarities are reversed between the thread and the wiring diagram. tjtheman007's head unit appears to have 6 RCA jacks. FL, FR, RL, RR for mids and highs and a pair for subwoofer L/R but he only chose to wire one of the sub-woofer signals. Why? Final question. I am not an audiophile of any sort; I am pretty tone deaf. Assume I do wire in this sub-woofer amp in through the RCA line-level outputs. What is a recommended cut-off frequency from the head unit for this Ford/Pioneer amp and subwoofer?