Too many idiots in this thread. I thought this forum was around to help those who obviously dont know enough to answer their questions.
Every 2.0L engine has EJ20 stamped on it. That includes the USDM WRX engine and the JDM STI Engines (including my V7 EJ207).
Check the timing cover (front of your engine, facing the radiator) and you should find a sticker. Let us know what the sticker says and we can hopefully identify the engine for you.
If you want to check if its stage 2, take a look at the downpipe. Does it still have the stock, uncut heat shielding around it? If so, there's a good chance its still stock because most aftermarket downpipes require the heatshielding be at least cut.
Posting a lot of pictures will help too.