No you don't need new pistons! However before you go slapping a Supercharger or Turbocharger on a 11 y/o engine you should run a compression check first to make sure everything is in good shape. Also be prepared for MORE maintenance, lower fuel economy, cost of the setup and stuff breaking. Any amount of boost can blow your engine if not properly "tuned". I assuming you have the 1zz engine.Forced Induction 101TRD Supercharger Kit is easy to install (about 8 hours) and comes with a pre-tuned TRD piggyback ECU. There are some used Kits floating around and the condition can vary. The SC runs off the engine serpentine belt. Turbo Chargers Kits are harder to install and require some expertise. You also need to have ECU piggyback and have someone "Tune" it. The Turbo runs off of exhaust gases and are a bit more fuel efficient. If you think about buying some E-bay Turbo kit and slapping in on and not doing any ECU tuning you'll blow your engine in no time.
05 Matrix XR 4WD and 03 Vibe GT
"If you want Government to solve your problems, then you are the problem!" BMSR
Trix MODS: SRI w/ AEM filter, Vibrant/Magnaflow Cat-back, Alutec Lightweight Crank Pulley
GT MODS: Cosmo SRI, DRL, Auto Stop