What makes a diesel motor 'peppy'?

[BoostnBenz]

At the given moment (soon to change) I have 2 300Ds, each having a different gear ratio but the difference is much more than that. My 83 had about a three second delay on taking off so I bypassed the overboost valve, it is down to about a half second. However it still doesn't have the low end pep that the 84 has, how could this be? What makes it peppy? The 84 is hard to hold back from squealing tires or throwing gravel, the 83 almost refuses to do either. Why? They both have about the same high end power, but the low ends are vastly different. The instant the accelerator is pushed on the 84 it is there, the 83 on the other hand if I hit it quick enough I can go to the floor before it really takes off. Why? What should I look for or do?

Thanks in advance,