What is this plug for?

Looks like fuel injector. But what it's doing that low.....

All cables up on the top of the engine block are plugged in. Every throttle body, every sensor, etc. All relays are done, there were no loose cables behind the air box. This is just one straggler right next to the relays, taped together with the fuse box cable. This harness isn't from my bike originally, so I suspect it's emissions as someone else pointed out. Thanks for all the inputs

Well... Go run it and find out what's not working! Maybe a seat warmer from another bike??? Idk