I can't get rid of this demon

[02Savana]

02 GMC Savana 5.7 4l80e 3.73. I have been chasing this demon since the day I bought this truck. I have replaced the fuel pump done the fuel injector conversion replaced the transmission checked and rechecked all of the wiring. My trans went at 90k and I replaced it with a junk yard trans. I can't say that it has ever run well mostly just adequate. It is very consistent in its inconsistency. On the rare occasion when all of the planets and stars are aligned it will run ok but never good. Now it has 102k and it is starting to do the same things that it did right before the last trans died. It has no power. I hit the gas pedal and it just goes waaaaaaaaaaa. It takes forever to get going. The motor wants to run but it feels like the trans is loading up or braking the motor. It doesn't feel as bad at less then half throttle but the more I press the pedal the more it feels like the brakes are put on so to speak. It revs up and starts to go but then just bogs down. Then I get this jerky hesitation thing. What is wrong with this junker?

[ejohnson03]

A simple , yet highler overlooked, fix is changing out the Fuel Filter.