Best lugging engine

[Running rough]

It seems to me the newer commen rail cummins with 2050 torque and @m*m^2 pull a bit better down low, the first generation of isx cm570 were totally gutless and sluggish under 1500 rpm, the low rpm response improved a bit on the 870, the 871 had a electric actuater on the turbo which improved response a bit, they all pulled ok if you kept the rpms above 1400 or so, the 2250 with their smaller turbo are quicker responding, but due to the smaller turbo can not build and serius hp, however with @m*m^2 and 2050 torque I would say the 2250 has almost cat like torque below 1500, just my experience, I may not know what I am talkin about