I just got my car from the U.S.
The car arrived and the first thing that goes is the in tank fuel pump on the first try. Not a chance to drive the car.
Bought a new pump from BMW dealer and the pump was DOA. (no refund...lost some good $$$$).
Then bought a Bosch fuel pump and shoehorned it on the factory (in tank) assembly.
Car started right away. Drove the car slowly (not pushing it) a little bit and I parked it. I had a meeting and had to go......
A couple of hours later I tried to start the car and and it sputtered, missed, bang, etc....after several tries it started but ran awfully.
Did some searches and watched some videos of HPFP symptoms and they all looked just like mine.

Started looking for a new HPFP..........

But I remember telling my mechanic when the car arrived that we should empty the fuel tank and put fresh gas. He said there was no need.......
I insisted.
So...We drained the tank.
Left enough to reach the gas station. There was black smoke comming out of the exhaust.
Put $20 of 95.
Now the car runs great. Starts as it should and runs pretty well.
Lots of power. No smoke. looks normal.
I hope it stays like that for a good while.