the different between gti n R3 on their perfomance is cam, ecu,exhaust system and body spotted (to improved handling)..their chasis are same either with gti,1.6 or 1.3..the difference only body spotted which gti have 100 over, n for sure R3 more than GTi..
and the advanti rims were 5kg lighter than stock GTi...
this is what was told by my fren to me...
hi bro
i drive a Satria R3, and i must say,
the stock engine that comes with the car (showroom) is stock like the GTi.
only difference is the extractor + exhaust system.
*engine wise*
cams and ECU is STOCK standard
body is extra spot-welded like you mentioned. :)