Mister T: the thread you posted does not bypass the factory amp but plugs the high side into the low side of the factory amp.
I dunno why all these companies have a hard time just selling a product that actually works.
Also,, I ordered those kits and ford actually used a couple different cables for the premium sound,, I found a 93' mark 94 thunderbird and 96 Tbird all had different connectors.
I've had even more of a time trying to find one to replace my complete cable (back of radio to kick panel and previous owner had cut the connector off it (jackazz)
for the time being I hardwired a non-premium connector onto it so it make hooking up a snap without trying to source a new cable.
Last note,,,, I bought a cable off scosche that has 4 RCA inputs and adapts to the OLDER style premium sound (like the ones in 90's Mustang or fords) but the new style has a CAT5 looking cable and nobody makes a RCA to Premium for that style so we can keep the factory and amp.