If you want to keep all functions on the oem radio, tap to the output of the Bose amp, which is in the right passenger kick panel. The outputs to a dsp to clean up the signal. I have a dsp/amp with a subwoofer output, which is easier but you could go with just a dsp into an external amp(s)...
I've heard of the issues with AWE but I guess my $130 spend on the install made it right. No rattles or movement from mine for about 2.5 years. Been on a track about 3 to 4 times so far. If in Miami I can recommend the shop. I do my own work but that was so cheap it's a no brainer.
Did both of mine for car audio purposes. Amazon has giid ofc battery cables. Negative is about 1 foot positive to alternator is about 3 feet.
Amazon link
https://a.co/d/jlC1X0r
Had my FL5 done, very slight difference. Seems a little more lighter turning the wheel. Call the service advisor to claim the part first, then go to the dealer.
I just installed a Audison DSP/Amplifier using all the outputs from the bose amp to the Audison dsp, it unfilters the signals to a flat. I've been tuning it and sounds damn good. Audison speakers and rockford subwoofer (might change). Lots of wiring and soldering.
Through the grommet in the firewall. Cut the hole for the main harness for a little extra room. I used an electrical that runs wire to get it passed the grommet.
I changed mine out to Audison speakers with Rockford Sub, on the Bose system. Sound deadening on all doors. Next is an Audison amp install, just waiting for it to get cooler out here in Miami.
Just received my TSP downpipe. Installed myself, fit perfect with AWE Touring exhaust. No issues. Replaced bolts and nuts with the titanium ones. Spray Krill oil worked great for stock bolt removal.
Take the molding and kick panel off it should be there. Then twist lock it back into top of the kick panel to lock it in. Put kick panel back on then molding.
Small knife just push the wiring harness to the side. If the grommet comes off, just push from inside and pull the tabs on it from engine bay. Not really hard, I stuck the tool to run wires and taped it, pulled through.