As far as i can tell, this is the relay that adjusts the fuel pump to run in high/low speed more. On the aem forum, the aem guy states that this should always be off because it turns on "low speed fuel pump mode". However, the wiring diagram would suggest something differant. This relay seems to bypass the resistor that makes the fuel pump run in low speed mode. Does anyone know what the correct functionality of the FM output is?

 

ok, turns out the FM output on the AEM doesnt seem to work on my unit (or something is broken/missing). I ended up just hotwiring that relay and I now get 13v at the fuel pump.