What is this piece?

[korey]

Bought the bike used and its not hooked up to anything. 06 S2R 1000

[herm]

thats your air sensor. it is normally connected to a little aluminum tab behind the headlight. but it does not need to be.

just stuff it back where you found it and enjoy the ride.

[korey]

It looks like it originally went into something because of that blue o-ring. Did it go to the airbox or something? I'd just rather do something with it than stuff it behind the headlight.

[Howie]

Looks like the air temperature/pressure sensor to me. 

[He Man]

barometric sensor.  aka pressure sensor.

[herm]

It looks like it originally went into something because of that blue o-ring. Did it go to the airbox or something? I'd just rather do something with it than stuff it behind the headlight.

HeMan got it right. its the pressure sensor. it originally was bolted to the wire U-shaped thing behind your headlight (page 58 in your owners manual.) if that is still there, you can bolt it back on. otherwise, there really is no better place to put it. mine (same bike as yours) has been sitting behind the headlight for almost 3 years with no issues.

[corey]

 

[Punx Clever]

That particular part number also happens to be used in some Italian made autos.  In that application, it is inserted into the intake manifold (mostly because they use mass airflow sensor and actually calculate how much air is going in vs guessing like ducati applications).

Gets air temp and pressure, passes it to the computer... based on throttle position and some slight trimming from the o2 sensor in the exhaust spits out how much fuel to spray.