W124 300TD power loss

[immoral]

Hi, my W124 300TD '92 suddenly lost it's power. In the morning everything was OK but after few hours it all started. I got back to the car, started engine, foot on the gas pedal and the car is barely moving When the engine reached it's working temperature i noticed that it got little more power, but not even close to how it should be
So after few days one person told me that i need to change ALDA unit. According to him this part "controls fuel pressure".

Can you tell me your opinion if changing alda would fix the problem, or i need to check something else to get my W124 running as it should be...