need more info...gas or diesel...mine had that problem it was one of the first symptoms of my fuel pump dying

 

Gas. Just changed my fuel pump 8-9 months ago. It doesn't start when first start driving truck. But starts when I try to accelerate onto the freeway. Could it be the throttle body.

 

did you put on a new fuel filter as well...so you saying it stumbles when hard accelerating like on ramp merging or passing

 

Yes, new filter and new pump. Even when I try to just go 3000 rpm at around 40 it doesn't really stumble it stalls, almost like what running out of gas feels like.

 

really sounds like its not getting enough gas...I`d look to do a fuel pressure test...get the test tool and you can hook it to a valve right on top of fuel rail near back on passenger side rail think 28-44 is normal if I recall