Just purchased a 2009 mustang gt/cs two weeks ago. I’ve began my normal maintenance when I first get a car. Oil, plugs, sensors, cleaning tb. I noticed a few idle issues and the car is running lean. When ac is on the idle surges down from 730 to 600 then to 900. The car also seems to have a hard time finding idle after rebind to 3000. The freon levels go up in down in the green but never lower or higher, clutch stays on for the most part. I also have a bucking issues when the car is cold and driving in first gear. I checked for vacuum leaks and found none. I checked for freon leaks with dye and found none. I’ve also notice one maybe two injectors are very loud. They still fire normally but are much louder than the others. I used the screwdriver technique to listen and it’s not from the valve cover it’s the injectors. This I believe is causing the car to run lean as the long term fuel trim is about 15. Lastly I checked the battery and it’s old but it’s still showing 12.4v.