Quite the box you’ve got there, dude.

“apex’i powerfc – $400”

Huh? It’s like “Name That Part“, but less fun. Apparently the seller no long needs it because he’s “gone aem ems”. Good for you, man.
Taking off our cranky confused old man hat for a minute, it’s pretty obvious from the ad this is some kind of engine control computer for a Nissan product. That’d be less annoying if it weren’t showing up in our search for whole cars in the “cars+trucks” section of Craigslist, which is completely distinct from the “Auto Parts” section of Craigslist. We wonder if the seller fails at telling colors or shapes apart as well.
At a loss, we plugged the title into the wordsmith.org anagram generator. Some results that may be helpful: “Face Wiper Pox”,  “Crappie Few Ox”, “Fox Carpi Weep”,  “Crap Wife Expo” and “Rape Cop We Fix”.
Wait, did someone say Fox Capri?