So I was sent over here from reddit to show you folks my exhaust setup. The 3rd cat and resonator were removed and replaced with an H pipe. Just past that is a pair of cutouts. They use a wireless signal, which you can teach the homelink to replicate.
https://www.youtube.com/watch?v=lR26FMKCxU4&feature=youtu.be&html5=1
http://imgur.com/a/H678q
https://www.youtube.com/watch?v=lR26FMKCxU4&feature=youtu.be&html5=1
http://imgur.com/a/H678q