I have the exact same issue to a T. I bought my 2011 Forster with 40,000 miles on it. Since day one it always had a burnt oil smell to it after shutting it off but nobody could ever find the leak. I've had the same garage change my oil for two years and now there is 128,000 miles on it. Yesterday at my oil change they told me The cam carrier seals need to be replaced to the tune of $2300. I don't understand how they could never find the leak and now all the sudden it's gonna cost me that much money. This is my fourth Subaru and for the first time I am very disappointed with them. It sounds like they have an issue here and they should recognize it and do what's right for their customers.