rough injector noise when accelerating

2004 Sprinter-

Had bad black death on #1 injector and a slight knock at idle on #3 injector. I replaced both injectors with brand new ones. Now there is no knock at idle but when I'm driving and putting a load on the engine the injectors as a whole sound rough. I would describe it as "breaking up" as the RPM's go up.

There are no codes, no smoke, no power loss. Do I bite the bullet and replace the other three or is there another reason I'm not seeing?

Where did you source the replacements? Its not unusual for questionable source "rebuilds" to have issues. I would double check the harness connections.

They are genuine mercedes, not rebuilds. Get them through a euro parts wholesale distributor

I would check your injector harness.

Would you describe the noise as knocking or pinging under load?

I would say neither a knock or ping. If this means anything it sounds like a powerstroke from the 90’s when reved. My other sprinters and the others I work on you just hear smooth engine sound (like a v8 being reved) through the rpm band.