I have a 2006 Ford Mustang 4.0 V6 that has been really good to me mechanical and pretty much overall. I have noticed that my battery light has been coming on. I have checked my voltage while my car is running its at around 14volts running so the alternator is charging. I have tested that battery its sitting at 12.5 after sitting for 3 days. I have noticed very poor acceleration almost like its not wanting to shift into a higher gear. I have noticed shaking as well as low idling and the car sounds different not as throaty. Gas mileage has went down a lot. I had an oil change about 1500-2000 miles ago with full synthetic high mileage oil. So I know it shouldn't need an oil change. The oil still looks clean too. I have had the Throttle Body and mass air flow intake cleaned and it definitely needed it. I am thinking spark plugs and wires might need to be changed. What else could it be? I'm thinking the low idle is causing my battery light to cone on so whatever is causing that is most likely causing everything I'm describing. I hope.