I should probably let the SRT guys handle this one, and knowing nothing about your car (you did not mention mileage, mods or any work done in the recent past, like if the pump has been replaced or upgraded), I have only one observation: You are describing how my truck acts on every "cold" start if I get in and hit the key.

If I get in, turn the key to "on", let it sit 5 seconds or so, THEN turn the key to start, the engine fires up right away and idles smoothly. Again, if I just turn the key to start, it will eventually start, rpm's will fluctuate, then things settle down after 10 seconds or so.

I also let the fuel pump run in the Crossfire until I hear it stop humming, and then turn the key. The XF will start up way easier and smoother that way. THe truck as 90,000 on it, the XF has 34,000.