If this seal is rubber, this might work;
at 205 reseal - Search

 

Not carrying EVERYTHING is normal. They only carry the most COMMON replaced.
As far as the oil/seal issue...I'd be more curious as to why the spark plug was leaking oil past it's threads, let alone why a rubber boot is there??
This is a first for me. Never encountered a separate seal in spark plug locations other than ignition coils/wires.

 

 

Interesting
Another stupid design IMO, but it is what it is. Great, another item I have to look forward to possibly replacing at some point

 

It was news to me, too, which isn't saying much... I looked it up to understand.

 

Not easily replaced if under the valve cover, as the illustration implies. Access being a challenge.

 

Just to be fair, the illustration is from the web, I’m not sure it’s the correct for 2.5L

 

Not at all easy location

 

Illustration is pretty much the same. It is okay. Not a bad job to do DIY. You also need the valve cover gasket and might as well do the other plug seal at the same time. Subarus been like this forever. 1999-2012 had the "EJ" tube seals. A 2012 Impreza with an FB engine still had the "EJ" type tube seals. 2013 to current have the new type. I don't imagine dealers having to do this kind of work frequently or there would be a recall. Look at it as free oil change on Subaru and your valve cover probably won't ever leak. Could be worse.

 

It’s not necessarily the part — it could also be that the mechanic isn’t available or is busy with other jobs. They have plenty of technicians who can handle things like oil changes or brake pad replacements, but not as many who are certified to open up an engine.

 

I tried doing the GDI intake clean by squirting the juice into the throttle body on my '23. A tedious procedure but near the end it started knocking fiercely. I tried to shut it down but it kept running until it finally died. I let it set & then fired it up. It seemed to run OK. Soon thereafter I saw an oil leak. I pulled the plastic pan & it was coming from the valve cover. Took it to the dealer who said that the spark plug tube seals were blown. While I was waiting, they tried to sell me a '25. Not knowing if I had maybe bent a rod or cracked a piston or set up some sort of failure down the road, I went for it. There was only $4K difference in the price. Just my story of the seal failure.

 

In all the instructions I've read and videos I've seen of using the GDI cleaning kit you cannot just go squirting it into the intake it can do severe damage. Mr Subaru Channel on YouTube highly recommends buying the metering tube kit that doesn't come with the chemicals it's another roughly 15 bucks on Amazon if I remember right. But if you did yours by just squirting that liquid into the intake you probably did potentially expensive damage. Maybe you were very gentle with it I don't know but it's not a good practice. That metering kit makes sure that no more than a safe amount is being dispensed in the intake. My private Subaru mechanic said the same exact thing, he's used those kits probably 30 or 40 times he figures, never had a problem and says they do a fairly good job but on higher mileage or really dirty intake valves might need a second treatment a while after the first one. His final comment to me was, but if you don't do it right you can be screwed.

 

"spark plugs in a recessed well" - thank you but NO! My first and last car with this idiotic design!
How to avoid?
Next car will be with the DIESEL engine...

 

Just back from service. The oil leak has been fixed under warranty. Here the parts if anybody wants to DIY

 

Not an easy repair; you need to lift the engine out of the vehicle to do it. I don't think you need to remove the engine, but you need to lift it several inches. Not fun!

 

OUCH!