Happened during a track session.Rotrex C30/74 10psi,AFR 11.8 EGT not above 817 Celsius.No intercooler,been running the car quite some time,approx 3 years
Cylinders 1-2 have been washed out from coolant.Just to clarify if someone thinks that they were lean(1 or 2) not in pair.3-4 looking good.No sings of pinging.The piece probably found it's way out through the exhuast valve.

 

can you get better pics and label each cylinder of both the head and pistons (of all 4)?

I wouldn't say 3 & 4 look good [too hard to tell]; they look full of soot and oil. And I see signs of detonation on #1.

what is your cooling setup like?

 

72° thermostat,il motorsport radiator(the big one) and coolant rerout.
I never had temp problems.

I had checked compression 2 years ago and it was at it's top.Apart from that oil in oil out it was a routine. Never missed a bit.If you look at the pistons they are genuine Mazda oversized.The engine had about 30.000 kms since overhauling.

The only sad story that might? caused the beginning of the end is that 3 years ago I purchased a FAKE E-manage Blue.
What happened is that during a WOT during summer,the piggyback lost its maps(fuel and advance)which led in a broken radiator and a burned coilpack.

Can't tell if that has to do in the situation I am dealing now.

Apart from that I am not sure for 2 things.
1)If my cylinder head is going to take care the abuse after rebuild and
2)What the F@ck happened...

Detonation in number 1 probably has to do with the missing part from the cylinder head.It was like pingpong between cylinder head and piston.

 

it's possible the HG failed when you overheated, would explain why that cylinder is so clean compared to the rest and the area between the cylinders just let go.

 

It looks like you're seeing a mix of earlier tuning problems combined with failed head gasket steam cleaning due to an overheating event.

My feeling is that so long as your tuning situation is fixed and you aren't overheating anymore, just take the head into a shop to be looked over and fixed if necessary and then put it back with a new head gasket. Everything should be fine after that point.