On sensors, particularly the MAF and to a certain extent the O2, they must be genuine Subaru. There are many tales of woe on the site about purchases on Ebay for less than half the list price that pleased the buyer no end but didn't fix the problem, and so they went on to another part of the engine thinking the MAF wasn't at fault. The Ebay rubbish is a hollow container that looks identical to the OEM part but just has a resistor and/or diode inside to fool the ECU into thinking the sensor is there. I opened a Subaru MAF and found it is a complicated set of ICs and other components which is likely why they charge so much. The problem with a lot of the the sensors, and our cars are laden with them, is that unless the connection is actually broken, they rarely give a CEL until they are really upsetting the ECU and due to delicate and sensitive nature of a MAFS, cleaning is not really successful or safe. AFAIK, knock sensors and down stream (secondary) O2 sensors are ok as generic parts though.
I don't know where you got all those part numbers from but different territories might carry an alternative listing although I did purchase one of my 22794AA010s from Chaplins Subaru in the US, where the S turbo isn't sold but the same part is used across the range. If it must be an OEM part, Import car parts are one of the better places to go and if a blue print part will do, they have those as well but if it must be the factory authorized item, they do not carry that in spurious form so shopping is pretty safe.
Look up a site called "Opposed Forces" which many of us use. You will find the S turbo in there, along with all the other EDM/USDM Subaru models, and will be able to find part numbers as well as cross reference them with components listed for Imprezas, sometimes using a different number but usually the same one, and are often the same thing but retailers carry the bulk of their stock for Imprezas and Legacys, so they don't list it as being for a Foz.
Always beware of 'sellers' selling the "listed part". The reason I recommend ICP is that I've never had a dispute with them but have with other vendors because the part they sold me was clearly wrong once I received it despite confirming by email prior to purchase that it was the correct component. On more than one occasion, ICP emailed me because they felt I was ordering the wrong part for my car, which I was once or twice.
