330Ci rattle at 2k rpm under load

Hi guys! I’ve recently joined the E46 club with my 330ci and I love it however I’ve only noticed recently after changing my pulleys due to horrific noise from them that I’ve got a rattle at 2k rpm only does it when engine is warm and only under load I.e. whilst driving and won’t do it when the car is stationary revved. Also sounds like it’s coming from the engine bay. I’ve google this and I see that it’s different for many people? Just would like to know what would be the main things to...

330Ci rattle at 2k rpm under load