my truck has just started doing this in the last couple of weeks and i am at a loss at what could be causing it. i need to change the fuel filter, but i don't think that is the problem. when i roll on it in 4th or 5th, it will pull hard to 2700 then pull back a bit then once it hits 2950 so it lays you back all the way to 4k plus. anyone have any ideas? i figure that it is not the fuel or it would not do so well above 3k. it is timed at 16 degresse and running 370's with a #100 plate just a bit forward. right about 430 to 450 rwhp. i will get a fuel filter this week and se if that makes a differance. just fishing for some ideas. mike

 

It's usually either fuel pressure (filter or overflow valve) or maybe the timing has fallen off a bit. If you bring the revs up in neutral does it stumble up high, or is it just under load?

 

check and see what your fuel pressure is around those RPMs and go from there.