If the only change is the injectors I'd suspect the wrong injectors were
installed, but there's another, more logical possibility.
'80s M-B diesels have a system to add extra fuel during acceleration; it
works on the turbocharger's boost pressure but if disconnected, or
otherwise not functioning the engine's acceleration is flat rather than
robust. I don't know your car's engine as these are not sold in the USA
but it may be similar to the older motors.