What is this and why?

I have a small curved plastic hose which comes out of my air cleaner assembly. It`s between my air cleaner and throttle body. It`s on top of the assembly (looks like a pcv valve, but it`s not), the other end snakes into the back of the motor, just below the coil pack for the 1 and 4 cyllinders. No connection, just fits into a round hole.
Mine was hanging halfway out, so I pushed it in all the way. Before I did this, the car had a slight miss and my check engine light was on, P0171 code and now the check engine light went off after I made a snug fit.
What is this parts name and any info why it would set off a code?

Thanks!

code P0-171 is for bank 1 running lean. The hose was a vacuum hose but I cant tell you what it was for because I'm not familiar enough with the impala bay to tell what you describe the other end was connected to.

Basically the hose being off or loose allowed the motor to suck in extra air behind the MAF. because this extra air entering the moter was un-metered the ECM doesn't know it's there and cannot compensate for it by adding enough fuel, hence your fuel/air mix was too lean. the O2 sensor in your exhaust sees that it's leaner than it should be and the ECM throws the code and CEL you saw. Running too lean can cause spark knock (detonation) which is very harmfull, so it's good that you remedied the situation!

Thanks for the info, makes a lot of sense. I read a lot about the p0171 code and what could cause it, about a zillion things. The car is running ok now, hope that solved it for good.