Acceleration rattle

Hello, I'm new to this site. I've got a 2001 E46 330i and just noticed a rattle when accelerating, there's also a smaller less noticable rattle when lifting off the accelerator after acceleration, for example between speed bumps, it seems to be coming from the engine bay and not underneath or the back. I thought it was a heat shield because it's a metalic sounding rattle but I've wedged the manifold cat heat sheild which seemed the most likely and it didn't seem to make any difference, I've also disconnected the disa which also made no difference. I've had the car on a ramp and couldn't see anything obvious, no exhaust brackets lose. I have to take the car for a drive to warm up before the rattle starts and it's harder to make happen when the car is stationary. I'm now getting concerned that it could be one of the manifold cats but I just wondered before I truly start to panic if anyone has any other suggestions. Thanks for reading and I hope someone can help.