I have an air/fuel meter on my 04 hemi, but I am not sure what wire on the O2 sensor I need to tap. Any help?

 

Is it a narrowband or wideband? If it is a wideband you will have to weld in a bung and then run a Bosch wideband O2 sensor. If it is a narrowband I don't have a clue. To be perfectly honest a narrowband is worthless unless you are looking for a light show. The range on it is so narrow that you will hardly ever be in the range. As an example the narrowband would display like 14-15 A/F and the wideband does 11-17. When you go WOT most people will be down in the 12's so it would never show on a narrowband. Hopefully that helps even though it didn't answer your question.