so my buddy has this truck its a good truck we've done a major tune up spark plugs spark plug wires distributor cap rotor button all kinds of sensors but the problem is when we're on the highway there is no over drive it looses power going up hill it doesn't want to accelerate. This is not the original engine its older and we do not know what year but it has the hookup for a mechanical fuel pump. Any ideas

 

I say that its a major tune up because he don't do much with it so that's why.