I have a 5.0L Coyote 2011 which has about 4300K on the clock. Over the past few weeks it is slowly getting worse after the initial start up of the engine. The initial issue started with a small amount of miss firing with a bit of black smoke coming out of both exhausts. what I have found is it does not matter if the engine is cold or hot but only happens in the first minute or 2of the engine running. if I start the engine and within 20 seconds start to drive off then the engine will misfire and have black smoke coming out of the exhausts. If I just start the engine and let it sit for about a minute then I have no issues and have full power. whilst idling it does misfire and runs rough as if it has a very lumpy tune. I have taken the O2 sensors off and found nothing visually wrong, spark plugs are good but black. I have 2 tune programs that i can use and have changed these over to see if this was an issue with no changes seen. Has anybody come across this issue before or know where to now look for the fault. Ta Dean