Hi all im new here on this forum and was wondering how I can tell if my used 05 stangs ECU has been flashed? it seems a little more mean than other 4.0L mustangs and has no engine mods.

 

Cant be done just by looking. You could go to Ford to "flash" back to stock strategy and then see if it changes...then you lost the custom tune if it had one. Without a new tuner from a reputable vendor and verified strategy that matches the code on the sticker on the CPU , (folow this link for how to find the sticker http://www.brenspeed.com/tech/cpucode.html ), you will have no way of setting up a custom tune at that point. So all that being said I would just drive it and be happy.