the rpm gage is moving up and down the motor is losing and gaing power

What is your question?

when driving you can feel the truck losing and gaining power its not real bad but you can hear the motor changing almost like its running out of gas or starving for air when i first got the truck it had plenty of power but slowly losing power it has 140xxx miles on it the previous owner did all the schedul mantinence i have had the truck for a few weeks and its slowly getting worst what can i do the check egin light came on ran the code tester it said random miss fire i have checked all the vacume lines i can find all good a random miss fire would cause me to lose power what do i do