Q: p1516 code on 03 v6 mustang. what should i ask to be fixed?

Although a diagnostic would have to be performed, the code you are reporting is usually a consequence of a fault in the intake manifold runner control (IMRC). To rule the IMRC system in or out, the recommended diagnostic is an IMRC inspection. The IMRC system provides a means of adjusting the flow of air through the intake in relation to driving conditions. The system includes a vacuum solenoid that operates a butterfly valve in the intake. During slower driving when the need for air is less, the butterfly stays closed. However, in aggressive driving situations, the butterfly opens and increases the amount of air sent to the intake. The engine computer compensates for this by adjusting the fuel mixture, and the result is an increase in performance. The system can get gummed up with deposits though and then the code sets. If you request the IMRC inspection, the responding certified mechanic will pinpoint the cause of the code and get the fault repaired, right at your location. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.