Just requested the PWS retrofit and Boombox install on my July 2019 build Model 3 Stealth Performance.
I have the speaker grill and pretty sure I see the wire harness secured to the frame behind the bumper on the passenger side.
Pending Mobile Install 7/29/22 along with a few other minor fixes....broken charge port pin and faulty trunk weather-strip.
Will update with details and cost after service visit.
Tesla PWS Retrofit