The top of the piston looks like detonation was occurring. Detonation on my boosted stuff has always started away from the plug towards the exhaust side. The thinnest part of the piston is at the top ring land to intake valve notch. I am in the process of gas porting my own pistons. We've been warned to stay away from the intake notch. from the info I've read lateral gas port is preferred on boosted applications. Looks like a lot of gas port holes as well. Everyone I've talked to says 10-13 holes. We just burned a piston in my sons turbo car at the intake notch. Though it was not gas ported.
Doug