Car missfiring? Only 4 out of 6 cylinders are working?

I got a 2002 Ford Escape v6 and it had a low idle and would die also I was getting 14 mpg. So I looked up some stuff to fix it so I changed my spark plugs and cleaned my mass air flow sensor( with appropriate cleaner) after all of that I started the car and idle was rough so bad the car would shake it was even hard to start up so I swapped and put my old plugs back in and it still is running like this we figured it was the injectors used a set of tools and heard them firing. The coil packs still fire does anyone have any ideas what's going?

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