Truck feels low on power when accelerating

About a month ago I started feeling that my truck felt as if it was running with half its power. When pressing the gas normally like I used to be able to do in order to get up to speeds in somewhat reasonable time, I find myself now having to put the pedal almost to the floor in order to get anywhere. I took the truck to the shop and they said that the ignition coil in the third cylinder was bad so they replaced it. I thought that should fix the problem, but I still have to step on the gas hard to accelerate even just moderately. Any one having this problem?

 

When were plugs changed last? MAF cleaned? Air filter plugged? All the cheap usuals checked first?

 

Don't think the sparks were changed in a while. And I am not sure when the MAF was cleaned, if ever. Air filter is not clogged.

 

Plugs. First thing!!!
Then MAF very well

 

Have an appt to get plugs replaced today. Lets hope this fixes it.