UPDATE !!!!!
Checked the fuel pressure with a fuel pressure gauge today, and she sits at 3bar constant, even when it stalls. ! So it's not the pump nor the Relay at Fault.(as i have by-passed it before, and makes no difference)
I have also changed/checked the coil, it seems it's not this either.
HOWEVER, When she stalls/cuts out, it lets out a right hard "Knock" as if it is pre-igniting, and then the engine spins anti clockwise !!! and then stops. It even ran for a second backwards which is seriously harmful.
Now, I had a timing light on the No.1 Plug lead today(between dizzy and lead) and when it cut out, the timing light went out, so it is obviously killing the spark somehow, which is causing it to stall. It's worth mentioning, the Distributor cap and rotor arm look like new, and no obvious signs of arc'ing out or cracks in them.
I've also had a tester on the coil, and she sees 12Volts on both sides, even when she dies.
Had all three crank sensors (on rear of engine, clip in at scuttle panel also)
out and cleaned them, but dont know if they could be faulty. ?? Anyway of testing them ? Remember, it can run fine for ages, and sometimes when it trys to die, if you rev it up, it stops it dieing. Are they expensive ?
Remember, the car can run fine for AGES, then just suddenly dies, trys to spin backwards and pre-ignite (i think) It's really REALLY annoying, as i'm really trying to figure it out, but no one has any diagnostic gear for an E30 M3
Any Ideas ? If you could let me know your thoughts it'd be most most appreciated.
Brian, not checked the O2 Sensor, the car does have a cat on it.
Also, it did used to run really lumpy when cold, but seems to have stopped doing that now, and runs fine from cold, but has this terrible problem of stalling/cutting out/pre-igniting.
