I just bought a 2003 Ford E350. It seems to misfire/sputter at all speeds, including idle but shakes badly at 55mph. If I turn overdrive off it seems to calm it down some but still sputters and shakes.

What I done so Far:
1. Replaced all the plugs
2. Replaced the Fuel Filter
3. Replaced the #6 Injector (I Had it tested and it said #6 was the problem)
4. Replaced all 8 Coils
5. Replaced Air Filter with K&N Air Filter
6. Replaced the Mass Air Flow Sensor

I am at my breaking point with this van. I keep putting money in this problem and it doesnt do a thing. PLEASE HELP!!!!!!!!!!!!!!