Here's what I've replaced: fuel filter, plug wires, plugs.

#1: Could it be a vacuum leak?
#2: Maf sensor or egr
#3:How do you test the coil pack to see if it's working properly?


I can put the pedal to the floor and it doesn't do much.....just stumbles!
My wifes corolla has more power than my truck! Pretty scary!

 

Look for a post titled "My truck bad loss of power" and see if any of the symptoms are the same as yours. It ended up being a broken harmonic balancer. The timing sensor reads off of it and when it is broken it really messes things up.