This is from my perspective as someone that has raced in SCCA, is now racing/doing HPDE in a prepared STi, and has built numerous engines. I've been doing things with motorized vehicles for over fifty years.
A story: A long, long time ago a guy built up a VW and then a Porsche for autocross. He built his own manifolds for a dual carb setup on a VW "bug". He ported the heads, installed an Isky cam, big bore kit and headers. It pulled wheelies. On a hot day, on the highway, he was showing off and outran a Corvair till the engine started knocking. It was toast. He had done nothing to handle the increased power other than tipping open the engine compartment lid (so it acted as a scoop). Moral of the story: You cannot start modifying an engine for more power without the having the supporting cast.
With the 818 kit's potential I can see many testing the boundaries of the Subaru engine. It is well documented that the engines cannot sustain extended hard driving or increased boost without modifications. Aptly named, "Rod Bearing Failure Nightmares/Stories" on NASIOC, it contains one post by Chris, the owner of Maxwell Power, that pretty well sums up the issues.

For any street engine I would recommend a better, bigger pan, a more effective pickup tube and a windage tray like Killer B offers. Moroso offers a 6.2 quart pan. There is not a cast STi oil pan. I think Brandon misspoke. I have both the KB setup as well as a smaller Moroso pan that holds five+ quarts. I highly recommend an external oil cooler. I don't think the stock one on the motor has much to offer.

For those that are going to flog their cars on the track I think you need all the above and must have something to deal with oil blowby. It is also well documented that oil goes into the heads at high Gs and ends up getting pushed out by blowby. The more boost you make, the greater the blowby. The cast pistons in STis are notorious for breaking when boost is upped and oil gets into the intake tract. There is a gargantuan IWSTI thread called The Official STi engine Venting, A/O Separators, and Catch Cans Thread!! If you can sift the wheat from the huge amount of chaff, there is a lot to be learned there.
I run a large external filter, large oil cooler, two quart Accusump and thermostatic bypass valve connected with -10 hose/fittings on my race STi, putting out 400 WHP. It holds over nine quarts of oil. I have a catch-can/separator that returns oil to the crankcase.
Since I will race my 818, and since it can generate a lot of G's, I intend to use a dry sump. I am interested in taking to anyone that has had experience with a dry sump system. More to come.

Finally, I heard that FFR did some research on oil pan starvation with the Subaru motor in an 818. Does anyone know anything about this?