Turbo
manifold
fuel injectors
fuel pump
bigger fuel pressure regulator
aftermarket engine management system
Wideband O2 sensor (for tuning)
positraction differential
larger exhaust
intercooler
blowoff valve
intake piping
rims and tires (for increased traction)
forged pistons
forged rods
cylinder sleeves
clutch upgrade (if it's manual)
wastegate (if your choose an external WG turbo)
some decent cams wouldn't hurt either
manifold
fuel injectors
fuel pump
bigger fuel pressure regulator
aftermarket engine management system
Wideband O2 sensor (for tuning)
positraction differential
larger exhaust
intercooler
blowoff valve
intake piping
rims and tires (for increased traction)
forged pistons
forged rods
cylinder sleeves
clutch upgrade (if it's manual)
wastegate (if your choose an external WG turbo)
some decent cams wouldn't hurt either