with 140,000 miles on my 2014 Outback 2.5 i decided to change spark plugs since they were never changed. Now, at times, it's idling rough and hesitating while driving. Not getting any codes or check engine lights. So, i took it to a repair shop and they changed #3 spark plug coil. Was slightly better on drive back from repair shop but same symptoms continue. Changed the other three coils and it did not resolve issue. Any ideas?