Strange engine sound

Hi all,

I've had an engine shudder issue before, so i've recently done a major overhaul of engine (see below of works done). My engine has this annoying rattle sound at low-mid RPM especially when letting go of the gas pedal after revving.

Works Done:
-EGR Cooler pulled and cleaned (I can see complete light on the other side, so it's definitely not blocked)
-EGR Valve pulled and cleaned
-All EGR Gaskets replaced with brand new OEM ones
-Intake manifold pulled and cleaned
-Air sensor on intake manifold cleaned with correct spray
-MAF Sensor cleaned with correct spray
-Engine intake carbon buildup cleaned (soaked with solvent and wiped off)
-Throttle body physically cleaned
-Coolant changed (Toyota SLL)

-4x Spark Plug changed (OEM)
-4x Coils changed
-New PCV Valve, New PCV Pipe (OEM)

Video attached is 3 consecutive revs in maintenance mode. Slowly going up in RPM and then letting go of pedal. Engine is unknown mileage but i'd estimate between 100-200k km? Different engine was put in car at some stage. Scanned using OBD, no issues or codes thrown. No issues with engine power or any dashboard lights. It's purely sound i'm judging by and it's definitely engine bay, sound is consistent when repeating similar pedal movements on the road, not just when stationary.

Is this normal due to engine mileage?

Also anyone know how to upload video to prius chat? Can't seem to get it on here.

 

It's a bit harder to hear it after I uploaded. But it's more audible in my original video I have

 

I think problem may be a clogged fuel injectors as this was not replaced, could this sound likely?

 

Hi Mendel,

about 600k km on body, but new engine placed around 450k-500k km. engine possibly had done 100k+ when it was put in, not a new engine, not sure on its history as this car was handed to me. I think could be either fuel injector or maybe the exhaust has come loose somewhere? Would this sound right?

 

Coolant level has been consistent and same level for years and has not been a problem. No issues with fluid leaks, im thinking might be loose metal somewhere but im going to have to do some thorough checks to confirm