67duetto

I have an 03 WRX wagon with PPP and a lit CEL! In 1st & 2nd it develops a misfire at about 5k. In 3rd it comes in about 5500. It has new NGK plugs, new MAF and new K&N air filter. Was the same before they were fitted. FreeSSM reports a P0559 error which it says is alternator output high. However, other sources say this error is brake booster pressure sensor circuit intermittent. When I clear the codes, it comes back the second time I start the engine. When I first read the codes it also had a P0546 EGT sensor code, but this has not come back. Which code meaning is correct and would this error cause the ECU to limit the engine?