Very loud noise from the engine

[Stiv]

Not sure if this is right section but here it goes.

About 10 minutes ago, driving TS as usual, I pushed the pedal to the metal to and some very lout ratteling noise camed from the engine.
I drove for about 2 minutes after that and even accelerating from a full stop in 1st gear gives this noise if i push gass pedal about 50%.
The car still pulls hard as usual in any gear.
My guess is transmission because rev in neutral doesn't give this noise.
But then again the car accelerates, handles and breakes as usual.
The noise is about as loud as the motor at 4000rpm to give you some audiable perspective.
But if i drive it really easy, there is no noise at any gear.
Btw. the car has only about 15000km on it.

What coul'd it be?
Please guys, help in any way you can.
If anything, tell me if i shuld drive it in this condition

Thank you