Upgraded Pistons

Pistons failed in some CAVE motors due to hydro lock or detonation.

Former was due to fuel getting into the ring groves and due to being incompressible fluid too much pressure was exerted (ring couldn't move up and down) and landings broke. That was attributed to bad spray pattern f the injectors and ECU getting confused thinking cylinders are running lean and flooding them with fuel.

Same situation can happen with oil or if coolant is leaking into the combustion chamber.

Detonation was due to fouled valves, sparks, injectors or piston crown causing glowing carbon deposits preigniting the mixture. No piston can withstand such a treatment. 

One changes pistons to make them withstand much higher temps coming with much higher power, to improve the "swirls" of the air/fuel mixture, to change compression ratio (higher or lower), to decrease the mass of moving parts by installing lightweight pistons (skirtless or made from much stronger alloys requiring less material. There are other reasons escaping me right now.

Unless you going above 300bhp no need for new pistons imho. Spend that money of getting a custom made exhaust manifold and better turbo.