engine bogs down and dies
 

i recently purchased a 1997 dodge 3500 4x4 cummins diesel with automatic trans it drove just fine the first 2 days i had it but as soon as i hooked my two horse trailer up to it and started pulling it around on any incline the engine would bog down and die you could throw it in neutral and it would return to normal can anyone let me know what i may be lookin at here is it air or fuel issue this is my first diesel and am learning on the go

i have replaced the fuel filter and lift pump still has this issue but truck randomly boggs down typically only does it when you stop and start to take off so it idles fine and most of the time will take off without a hitch but every now and then it acvts like its not getting fuel and the more throttle you give it the worse it boggs out any ideas