There could be various reasons for this loss of power. Drawing from a similar experience we had with the 260E, th ultimate fixer was replacing the accelerator cable. But in our case, it was a constant high RPM at idle albeit the power was not the ultimate one could ask for.
Perhaps it was also replacing the injectors which made a big difference.
Our fuel pump and filter was good.
So perhaps you mght want to start with the fuel system and pump before moving onto the injectors?
126 tailed by a 203, 129 leading the pack.