Audiology

Hey, any ideas for what to do with stock parts: exhaust (cat and downpipe), shocks, coilovers, disks, calipers from a 2013 A3? My husband upgraded these systems last year and now the parts are taking up space in our garage. The car had about 32K miles on it when the work was done.

Would they sell on Craigslist? Would my local independent garage want them? Would a local auto recycler be interested? Could we use these if needed on our 2006 or 2007 A4s? Or is this basically scrap metal? (I'm guessing the catalytic converter can't just be scrapped, or can it?)

Thank you!