I'm having a hard time finding a wiring diagram or harness adapter to tap my sub amp into. 2016 Highlander XLE without the upgraded JBL audio. Can anyone help me figure out where I tap the subwoofer amp into the stock head unit for power trigger and audio source? A wiring harness adapter would be cool also but not necessary if I can determine where to tap into on the stock radio harness. I'd be super appreciative.