Installed my trail pipe a couple weeks ago. The sound is very subtle like you said. Barely hear the difference inside the cabin and outside, just slightly at cold start and low RPMs.
Yes, you can. Your friend would have to get an AI box then plug it into the port the normally takes Carplay/Android Auto. Also you would need to tether internet from your phone to that AI box.
I've had the OTT tune on my 5th gen and have brought it into 2 different dealership, they never noticed the tune when they're doing their diagnostics. At anytime you want to remove the tune and go back to the factory map, you can get with the original tuner to do that. I'm looking forward to do...
I just installed mine this afternoon. The quality is good but not the fan of the hardware, I think it could be better. It took me roughly an hour and half to do all 3 skids. Overall, I’m pretty happy how they look.