Car reving up and down need to clean a idle.

Located on the opposite end of the intake from the throttle body. There is a long air tube which comes from the intake and runs back toward the throttle body. The Idle Stabilizer Valve is a metal piece that turns looks like an elbow, as it makes a 90 degree angle in the air tube. (The dealer wants about $400 for these. Ouch!)
Also be sure to clean the throttle body as well.