I've got about 1100 miles so far on my 335i Msport.
It's seen red line a number of times all ready, along with a few full throttle accel runs, all well before 500 miles on it.
No WFO from standstill yet, but very soon.
Within the first week of getting my car I did what I've done with all my new cars and bikes.
I do a moderate slow accel to redline in 1st, then let engine braking bring it back down slowly until around a bit above idle, then 2nd gear accel moderately slow to red line and let the engine slowly decrease revs, repeat with at least 3rd and as much with 4th as speed conditions allow.
The purpose is to let the engine run to it's maximum rpm and then let the natural vacuum and friction bring it back down, thus allowing the rings to fully do their job and mate well with the cylinder wall, and for all the engines whirrly bits to get full rev and mate with each other. This is one area where you don't want "loosening up". Piston rings help provide the needed seal for maximum compression of the air/fuel mix, which leads to best efficiency and power production with least blow by, meaning, keeping the oil away from the combustion chamber, and keeping the gasoline out of the oil supply. Keep all the bits happy and working in harmony.
This engine has shown itself to be very strong and powerful. It feels even stronger than the N54 in my previous 135i. This 335i is a bit heavier than my 135i, yet it feels stronger and faster. I got a good one and want to make sure I give it a good initial wear in.
The only thing I don't do is WFO standing starts all the way to red line a la drag race style before 1000 miles. After that, it's ON!