05 6.0 Acting Very Strange

[cryango]

I've got a 2005 F350 6.0. It's got a banks 6-Gun Tuner with Speed Loader and a Magnaflow Exhaust. Other than that stock. This morning I'm at the gas statation and fill the tank ($4.99/gal in Santa Barbara in case you're wondering). I get back in and the truck won't start, starts but dies after 2 seconds, won't start. Process continues for 15 min. Finally it starts. Drive to work, no problem truck runs fine. Get back in the truck to go to lunch, starts right up but now the check engine light is on. Running/Starting fine, but now i've got this CEL on. Any suggestions where to start looking ?

[BigRed]

Check engine light...