AFAIK, all EJ25 block use that lettering. Not sure about any other EJ-series though. I never bothered to look as I've never owned one. There are quite a few differences between EJ255 (WRX) and EJ257 (STi), S(ingle)-AVCS vs. D(ual)-AVCS are one of them. Internals were slightly different, STi ran slightly lower static compression, and then there's the external differences like turbo and intercooler.Correct. I was aware of the what the letters meant. For some reason I was under the impression that the WRX case halves used different lettering. It is a single AVCS engine. Could that be what makes it a WRX engine and not a STI engine?
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