Rudy - I'm not 100% up on ST but I think I can answer at least this much:

coatings of the usual sort are allowed. this is approaching an all out engine build class. coatings belong in that, philosophically. I think some STAC guys have commented in the affirmative about this in another thread.

11.5CR of the 2ZZ-GE is allowed as that is stock compression. older rules used to read something like "11:0 or stock if greater" but now they simply call the specific engines allowed with non-standard specs on spec lines. interesting situation with the engine being part of a car that is "disallowed in its entirety" while also in a mass produced celica etc... there's no difference between them that matters to the rules that I am aware of. if there is, use the Toyota-sourced part. the 2ZZ engine is SPECIFICALLY allowed, as specified. why on earth would you run it @ 11.0:0 CR?

the VW ABF (Euro market) is listed in the spec lines. there has been an allowance for non USDM motors for ~1 year, on a case by case basis, with approved motors to be listed. see 9.1.4.G.3 (STCS) for details. Go ahead and request a 3rd or 4th gen (BEAMS) 3S-GE, a 20v 4A-GE, etc... worst they can say is "no.

the STCS main and STL sections are silent on allowing dry sump but do say (9.1.4.G.11.) that the OEM an OEM type replacement oil pump shall be used. if the car CAME dry sump, keep that system, otherwise, stay wet. You can also change pickups etc.. as detailed.

ST is not IT. splitter rules are as described for each class. if you run an IT car in STL as an IT car (NOT a "10/10th STL vehicle") you run an IT splitter (wheel-limited) and all other IT rules. if you are running a car built to STL rules, you run the ST splitter (3in). there are a lot of differences between the IT and ST splitters, btw.