random engine miss fire still!!!

Is the forum search working? I have a random engine miss fire with the Error code P0300 from the testbook diagnostic.

The car is a new addition and is a 2002 MGTF VVC160

I have done the following:
NEW
(1) coil pak
(2) ignition leads that come with coil packs
(3) correct spark plugs

Run the above 3 items through a race diagnostic tester and they exceed set standard

Replaced thermostat
replaced temp sensor
drained and refilled with red coolant
bled cooling system at ALL points

The random miss is ANY and ALL cylinders

Takes about 10klm to show. Engine miss fire is at:
low revs
or high revs
or mid range revs

have checked for leaks in induction and exhaust

using NO coolant

No coolant in oil
No oil in coolant

No signs of weeping on the block

So engine miss fire is only after the car is hot. Car is carefully warmed before exceeding 3000RPM

engine will Rev past 6000RPM

engine warning light flashes and goes solid. I can keep the miss fire away after this if I increase RPM carefully. But the engine light is still on.

Park the car and come back in 60 minutes and NO miss, NO engine light. And start all over again.

I have only the O2 sensors to go. Are the O2 sensors the same Up and down stream? Are they 4 wire. What brand of sensors can I use.

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random engine miss fire still!!!