I have to keep my foot on the throttle for a couple of minutes and after rpm fluctuate between 300 and 500
What @yaser said, and I would add, clean the IAC, Idle Air Control
https://www.youtube.com/watch?v=C98wZDnjuE8
Have you cleaned the MAF sensor and throttle body?
Sounds like the IAC valve. Those are prone to fail on the New Edge Mustangs.
I would do everything suggested already in this thread. I have a feeling between @yaser and @toyotagrl you will resolve the issue.
About the only thing I would add is if you clean the IAC valve and still have issues, go ahead and replace it (cheap part) and see what happens.
@yaser @toyotagrl @Mod_Man thanks guys. Sorry for the late reply, been busy. I swapped out the iac and it starts right up, drove it around for a bit last yesterday and now it idles rough and won’t accelerate even if I floor the pedal after I swapped the new valve in, I haven’t had a chance to thoroughly check if I accidentally disconnected a hose or something and didn’t notice.