My W124 E220(M111.960) has trouble starting when hot.

Symptoms
1) When car is hot/warn I need to crank longer.
2) When car starts it shows symptoms of miss-fire, feels like only couple of cylinders have fired, Pressing accelerator fixes the issue.
3) I don't see this issue when Re-starting interval is short ( < 1 min).

Diagnosis
1) No error codes
2) Fuel pump starts humming when fuel level is low ( < reserve), otherwise operates normally.

Solution ?
From what i could gather from previous posts is, it could be
1) Fuel pump ?
2) Accumulator ?
3) Injectors ?

• How do I check which injectors are bad?
• Will cleaning do ?
• Is replacing injectors DIY?
• What other parts do I need if I have to replace injectors?

Thank you