I have a lovely smooth running replacement 1.6 diesel engine in my van. It is only doing 50mph absolutely flat out. I don't want to mess with it too much 'cos it is so smooth and quiet

I just need it to be a little more lively. I have the original engine with the fuel pump and injectors etc. Is there a chance that I could get more power and response by using the pump and injectors from the old engine? This was replaced 'cos it blew a hose, possibly due to head gasket failure. (It is also a 1.6).
I don't want a fantastically high speed, just to get to 50 a little more quickly, and then maybe creep to 60-65ish!
Any sensible ideas/replies welcomed.