Great work on the shell mate!
Yeah the graph tells the story.
You can see by the boost plot & torque curve the wastegate has control by 2600rpm. This means you have reached the max turbine flow by about 2600rpm. The wastegate can usually give you another 15% at least or so on top of that depending on it's size then when you hit that limit the back pressure is going to really ramp up & start to cause reverse flow in the combustion chamber as you have more exhaust pressure than intake killing power.
The drop in power reduces exhaust flow but you still have so much back pressure due to higher revs that the wastegate is forced open. The two combined causes the boost drop in your case because we know the compressor can flow enough air for that power.
A restricted exhaust flow creates high EGT's combined with the slightly lean mapping on that graph that again causes high EGT's is what killed your piston due to detention caused by extreme EGT's.
You have stuck a turbine section intended for a 2.0L engine onto a 2.9L.
The bleed valve reduces the boost pushing on the actuator so it can withstand the back pressure for longer.
However you will see the same happening again just higher up the rev range or if you run more boost.
Also the turbo will never make the same power on the 2.9 engine it can on the YB, the turbine will limit it just like the washer's fitted to restricted mopeds!
