It's a first generation AEM EMS for an EVO 8. The part number, 30-1313, is the correct part number for your application. This ECU, in my personal opinion, is the best ECU on the market. If you decide to sell it and go back to stock, please note that the AEM ECU is very expensive...

AEM ENGINE MANAGEMENT SYSTEM EMS 03 MITSUBISHI LANCER EVO | eBay
whereas the stock ECU not as much...

eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low pricesAs far as the check engine light with the AEM, unless it was a programmable output, it shouldn't have came on. Perhaps your tuner set it up for safety in case certain parameters get out of spec?