Air/Fuel Ratio Question
 

What is the ideal air/fuel ratio for the 4.6? How do you have it checked?

It is checked during a dyno run and costs an additional 10-20 bucks on top of a basic dyno run. The A/F ratio is best when it is around 12.5:1 to 13.5:1 from what I have been told. Abit on the leaner side is said to be better. I'm new to this and have just asked this same question on another board. Hope this helps.

the optimum a:f ratio is the one that makes the most power with the available fuel without detonation. this can only be determined by monitoring/adjusting during a dyno tuning session. every motor responds differently to timing and a:f changes.

people like me that run a power adder, typically run a richer mixture for safety reasons, while naturally aspirated combinations can be tuned closer to stoichiometric ratios.