Subaru Forrester was misfiring and sputtering as if it was going to stop running. The car was shaking. Had car towed to Subaru dealer for Service. At first we thought Spark Plugs and Ignition Coils but this did not fix the issue. Service determined a spring valve was broken which caused the issues. I have escalated the issue with Subaru Corporate, waiting for their response. Other Subaru models have had this issue with the spring valves.