Grinding noise under hard acceleration (over 5k rpm)?

[kyrix1st]

I'll snap a gopro in later for a more detailed video,

but my z3 1.9 (M44) makes a grinding noise on full throttle after 5,000 rpm.
If I shift up, it goes away so I think it has to do with engine load.

I'm guessing it's drivetrain noise but can't determine which part's causing it...

I've changed flex disc half a year ago, and changed diff fluid yesterday.
Car is only driven once a month, so some parts may be rusting.

[Vintage42]

Maybe a broken motor mount allowing the engine to move under torque and allow it or the header contact something.
But max torque is at 4,300 rpm, so I would think the noise would appear before 5,000 rpm.
And it would not sound like a grind in the drivetrain. Is grind the best description?
Did the flex disc still look OK, bolts still tight?

[BimmerBreaker]

Probably just the 4 cylinder screaming for dear life

"why me!!!"
"Why!!!!!"

[Vintage42]

My 4-cyl revs to redline sweetly. The little engines need and love revs.

[kyrix1st]

I am leaning towards failed flex disc by dealership installation. Time to claim another flex disc...

- - - Updated - - -

Probably just the 4 cylinder screaming for dear life

"why me!!!"
"Why!!!!!"

Becauseracecar

Maybe a broken motor mount allowing the engine to move under torque and allow it or the header contact something.
But max torque is at 4,300 rpm, so I would think the noise would appear before 5,000 rpm.
And it would not sound like a grind in the drivetrain. Is grind the best description?
Did the flex disc still look OK, bolts still tight?

Engine mount was changed along with tranny mount 1,000km ago.