idle at 2k need advice

[180sx+silvia=sileighty]

Hey guys, just last night my car started idle at 2k when i come to a complete stop. The car runs fine. But it is loud and annoying me. I used the search and people are talking about the IACV and VAC. I dont know what these term mean or where its located to fix my problem. Im just trying to get it to idle like it use to before last night. Before i was idling at 700-800. i dont know what happened. any help or advice for me. let me know thx guys