The VANOS unit is BMW's variable valve timing system, consisting of a pump and soleniod and rotating the camshaft to make more torque at various RPM.
Having a variable camshaft makes the S54 engine generate more power in high RPM ranges without feeling too sluggish in lower RPM ranges.
A failing VANOS unit will affect performance and cause misfires, rough idle, engine codes, poor MPG, and compromised performance.
Product is a complete S54 VANOS unit by BMW