Burning rubber smell after kicking down

[peterjaw]

Hi all,
My 07' X5 (e70), 3.0Si, has a strange phenomenon. Everytime I kick down the accelerator and reach speed at about 160 ~ 170 KM/Hr. (100 ~ 105 Mile/Hr), right after I release the padel, I can smell something like burning rubber or burning oil.

The harder I kick down the strong smell I will have. That means if I accelerate the car gently, then the smell is not so significant; but if I hit the padel hardly, then I will have strong smell.

The dealer has checked the enging bay and did not find anything leak, they can't help on this issue.

Does anyone have any input about this issue? Thank you very much.