I did my install on a 2020.
I think Taco tunes amp plug and play harness includes wiring to run to an under seat mounted amp. I wanted to use speed wire for a cleaner install so I got the sub harness and cut off the connectors to make my own harness. For me purchasing the cheaper harness was...
The 2020+ 4runners have all the speaker wires on a single connector with nothing else on it. this makes it easy.
The tacotunes harness has standard car audio colors on their side of the connectors that lined up with my amp harness colors. super easy. I spent time before getting the harness...
Tacotunes has a harness to add an sub to a 2018+ camry. This has the male and female connectors you need to build a t harness and it goes for $35
I just used one to install a Kicker Key 200.4 to my 2020 4R.
link: 2018+ Toyota Camry Add A Subwoofer Harness - PLUG n PLAY - Taco Tunes - Toyota...
In a related question:
Would this Camry harness from Tacotunes work to create a t harness for hooking up an amp to a 20-21 nonJBL 4runner?
2018+ Toyota Camry Add A Subwoofer Harness - PLUG n PLAY - Taco Tunes - Toyota Audio Solutions
I'm looking to wire up a Kicker key amp like the OP and not...
