I have a 95 3.0 M3 which starts in the button and runs fine
Then after 5 mins on the drive or 2 mins driving, it drops a cylinder.
But it doesnt just lose 1.
It will go from 6-5-4-5-4-6-3-6-2-1 die.
Its really weird. It first started that it lost 1 cylinder, byt would carry on drivin (badly of course) park it up for a couple of hrs and it would b fine again, for ages.
Gradually it got worse, more cylinders started droppin and it happened sooner and sooner, till now. Its totally undriveable.
Strange thing is sometimes the cylinders pick back up for a short while.
Then leave it over night and it starts fine again.

I have had it on a launch scanner and theres no fault codes stored,
Tried a different ecu off another 95 3.0 m3 thats known to work,
Different coils,
New crank sensor,
New fuel filter,
Different afm
Different tps
Also read live data from sensors when it plays up and all seem ok.
No mayo in oil/water
No lack in performance when it works
No smoke/smells
Not losin oil/water

Engine was rebuilt 10k ago
Everything was perfect before this.

Any1 got any ideas? Ive got a spare car that works i can try parts off.
Any ideas before it goes into a specialists?

Could it be fuel pump related? I would say it was if it only happened under load, but as it happens on the drive at idle it makes me think not. Especially as the cylinders pick back up sometimes.