BK8100

'16 AT Mustang GT W/90K miles stalls at idle and the rpms rev high and stick momentarily when letting off the throttle, more so when cold. Mechanic replaced MAF sensor, passed smoke test for leaks, no codes. Worked good for a week or so, now its right back to same issues. 0.5-1.7lbs air flow rate at idle, around 11lbs at 2500 rpm. Mechanic wants to check the new MAF sensor to see if its faulty, Im trying to load up on ideas before they look at it again. Any ideas would be appreciated.