To help me help you, please specify what system or component you're referring to. For example, are you looking for:
* An orifice in the fuel system? There might be small orifices within fuel injectors or in the fuel pressure regulator.
* An orifice in the PCV system? The positive crankcase ventilation system might have small passages that could be considered orifices.
* An orifice in a vacuum line? Restrictive points in vacuum lines could be described as orifices, although they're usually just smaller diameter sections of tubing.
* Something else entirely?
Give me more context, and I can provide a more accurate answer.