Well, why do you think it now needs pistons, rods or something serious? Can you add a few more details?

Now....IF it's a melted piston or something indicating serious engine damage and the shop that it's now at can't figure that out by known, obvious methods of engine fault tracing, then it's time to get it out of there and have another opinion.
Melted or damaged piston(s) would be obvious because you'ld lack compression and doing a simple compression and/or cylinder leak down test would determine if it's related to pistons.

Btw, too much boost can and will destroy and engine so if and when you get it back and it's fixed (running), by all means turn the boost down to safe levels. Did you use a calibrated boost guage or did you just guess?