I have a 2017 Forester XT 2.0 Turbo which developed an engine noise that at first I thought was ignition knocking, because the onset of noise was during summer and it had not occurred earlier in the year. The noise manifested itself only at full throttle and high rpm -- which made me very alarmed. Despite chats with at least 3 Subaru dealer service advisors, no one came up with a better suggestion than "don't use Costco fuel".
In August, I myself was underneath the car and noticed the attached photo appearance which immediately suggested to me a possible exhaust leak. I now found the service advisors at least agreed I should bring my car in.
The surprise ending is, Yes I did have an exhaust leak, but NO it was NOT what shows in the picture. They wire-brushed the flange shown, and convinced themselves that is not a crack, just a casting effect. (I still don't think much of it though).
Our exhaust leak was not at the photo location, but rather at the right-hand cylinder bank exhaust manifold, where they told me a nut had backed off, and then allowed the gasket to fail.
I'd be most interested to hear if other FA20 Turbo engines are similarly misbehaving. Has there been a engine assembly problem with inadequate bolt-torquing? Or poor design of exhaust manifolds? Or poor metallurgy??
I'd also be interested to hear whether other FA20 Turbo engines have exhaust flange castings which look as bad as my photo. Has anyone actually had a failure in this location? (immediately downstream of the turbocharger)