you have to loosen up the ALDA on the pump and then also work the vacuum modulator and bowden cable to adjust the shifting points and softness of the transmission.
The 617 will pull pretty nicely. Being in Pakistan its not very uncommon to see badly adjusted valve clearances on diesels, It would be beneficial to buy two spanners and have them bent by a welder to adjust the valves properly - DO NOT USE straight spanners as it may break off a valve guide (you wont like it)
so - first things first, check valve clearances, check pump timing and timing chain wear and verify nozzle break pressure.
Everything good, now you can work the pump and tinker with boost