I joined this forum just to thank you all for discussing this issue... and to say that the leaking intake manifold gasket is definitely not limited to 2008 or earlier (or whatever the latest year mentioned in this thread so far). I'm really surprised that I haven't found many, many more threads about this issue elsewhere on the net, given the number of vehicles that must be affected.
I live in Tokyo and purchased a 2011 Subaru Legacy 2.5i EyeSight Sport Selection in 2020 with only 45k km on it (not uncommon here in Japan). The first winter I owned it, I experienced the exact same problem (runs fine until the blue light goes out, then hesitates until fully warmed up). I wasn't about to mess around with dental picks, etc, so I paid a mechanic about $200 to change them for me... a good deal for me, given that he said it ended up taking him about 5 hours. The original gaskets were black rubber, thinner, and much harder than the replacement gaskets (14035AA492).
The difference is night and day. No more hesitation, and I'm pretty sure that the car is running much more smoothly at any speed or temperature.
I just purchased the exact same model from auction and am shipping it to the UK to use there; I haven't even driven the thing but I've already bought the gaskets and will get them changed out as soon as the car arrives.
Thanks again.
