I am currently working on this 07 taurus with 127000 miles on it. customer was complaining of rough running. no codes are stored-- but mostly feels like a slightly rough idle. i pulled the air cleaner box while it was running to check maf. thats when i noticed a popping noise through air tube to box. other internet searches listed emi as a possible cause. the first thing i thought of was alternator, so i unplugged it and the popping noise and rough idle went away emediately. installed new alternator, still does it. has anyone out there have any ideas, thanks keith