You should do a search. You will find tons of info.

 

Search results in this forum using keywords 'turbo' and 'upgrade'.

You'll see that the IHI VF30 and VF34 (ball-bearing variant of VF30) are common upgrades with a few larger turbo choices that will bolt onto factory and replacement exhaust manifolds and downpipes. Even larger turbos can be used if you are willing to fabricate the exhaust.

Turbo choice depends mainly on your intended usage. The smaller turbo upgrades will retain stock-like driveability while larger turbos tend to move the peak power higher in RPM and making the torque band narrower. Too big of a turbo will result in 'soggy' bottom end torque with power coming on like gangbusters way up in the RPM range. Cars can sometimes be quicker to accelerate when the torque curve is wider, instead of peakier. Tuners with off-the-shelf upgrades tend to put together packages that concentrate on the area under the curve on a dyno printout of torque output.

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