2006 mustang

2006 Mustang GT Coupe Lets start at the very beginning Bought the car a couple months ago for a steal. Had no catalytic converters. Too loud and wanted to avoid future issues with smog, so I sourced an original catted h pipe with 34k miles on it (Car it came off of currently has 40k miles)...

I recently got an aftermarket head unit and i have everything installed and i realized that the antenna cable does not fit with my new aftermarket headunit. The headunit takes a moterarola style. But i cannot for the life of me find an adapter for it.

I was changing the 2006 mustang trans filter and ran across this small piece of plastic cracked. Anyone know what it is and if i should be worried