There is an 'A' and 'B' connector on the amp, 'A' has pins 1-12 ( input connector ) and 'B' has pins 1-18 ( output connector ). My only question is : do you put the capacitor in series on the (+) or (-) to the left & right door speakers ?

( pins 8(+) and 18(-) are the left door and pins 7(+) and 17(-) are the right door speaker )
and yes, the amplifier is in the passenger side floor well under a metal guard, easily accessable.