I have a 04 Mustang V6. The original 3.9 was blown and swapped for a 2001 3.8. It's been a couple years and dont remember exactly what year but it was a 01 or 02. I have drove it for 2 years and the entire time it has had the problem. Everything on the car works. It cranks, idles, and drives fine until you take off from a stop or you try to even gently accelerate at any driving speed. When taking off from a stop it will run fine thru first gear and then usually half way thru second gear it will loose all power. It will stay at the same mph no matter how far you press the throttle. If you are already at normal driving speed and try to speed up it will do it then too. And if you press the throttle harder it will even down gear and the engine will rev higher but will stay at the same mph or slowly lose speed. It normally last for around 20 seconds and then the power returns instantly and it has the power it should normally. During both instances the check engine light will flash and as soon as it stops flashing is when the power comes back. The only codes it throws is a misfire on 2 different cylinders and sometimes a random misfire code. All plugs wires and coil pack have been changed with no difference of the problem. Also when running the AC it will stop blowing cold and blow warm while the light is flashing. It turns back cold also when it stops flashing and power comes back. Any ideas??