Is a STi just a WRX with a bigger wing... No.

For your early GD models (2002-2005) you get:

EJ207 semi closed deck vs EJ205 open deck
VF35 turbo vs TD04
550cc injectors vs 380(?)cc injectors
6 speed gearbox vs 5 speed (DCCD in 2005 too)
Better diffs
R180 vs R160
Bigger TMIC
Brembos + larger discs vs WRX 4 pots with smaller discs
5x114.3 PCD in 2005 onwards
Not 100% sure if factory or option, but then there are things like trailing arms, bracing, sway bar sizing etc etc
+ a whole lot more

Oh, and you get a bigger spoiler.

__________________
[COLOR="Gray"]550Nm off a 2L... Just wish it was in the dak dak...[/COLOR]