Hi guys
Sorry for the long post but I was wondering if anyone could help me troubleshoot a noise.

Basically when the engine is at low rpm but under some load (low to medium throttle seems to make the worse noise) I'm getting a mild metallic rattling style noise from the front. Can hear it in the car and quieter outside the car. Doesn't do it at idle or revved up in neutral. Seems to do it worst in 4th and 5th gear. It can't be heard at all in 1st and 2nd gear, bit more in 3rd but much more noticeable the rest.

It almost sounds like it's coming from the left (transmission) side. My drivetrain is very clunky anyway when changing gear and engaging the clutch but the clutch and bearing are all new Volvo 850r and bites fine no juddering.
Engine is newly rebuilt now done 700 miles (500 of which were very light then oil change and now some full throttle and higher rpm driving). All bearings are Volvo and sized as per the markings on the crank and block. Engine is bored to the size of the Pistons (83mm now as bores were worn) and new rings. New forged rods (max speeding) and big end bearings (Volvo). Top end has only had lightly ground valves and new stem seals. Only other thing not replaced were gudgeon pins but they seemed to fit in with a light thumb pressure.
New timing belt kit, damper and water pump from Volvo.
Timing is apparently 7% advanced according to the tuners laptop. Knock sensors are not being activated at any point. No problem codes. Stock tune. Running shell optimal fuel. Using 5w30 Castro Gtx oil currently with an aim to go to Fuchs 5w40 in another few hundred miles.
Engine runs fine no large vibrations or harsh knocking noises, compression is 150 over all cylinders and uses no oil or water to note.
Changed oil in transmission (Volvo own) but not replaced driveshafts.

I wonder if this noise is actually from the transmission or turbo rather than the engine. Turbo is stock and not been reconditioned but seemed to be working ok however Wastegate was quite loose/wobbly when disconnected so could this be rattling as it begins to open or close? Seems to make the most noise at low rpm but when boost is about neutral beginning to build into low positive figures. More throttle worsens the noise slightly and full throttle if anything may quieten it.
Iv tried to get a video of the sound but it is so hard to hear it's hardly worth listening for.

I'm fairly sure the old engine (which wasn't rebuilt just removed) made a similar sound but can't be sure.

Do they just make this noise??

Thanks very much!