Allright guys, it's time to upgrade my suspension - and I've done quite a bit of research. Here are the main differences I can find as far as items worth upgrading/items that should be upgraded to bring the car as close to ITR spec as possible:

Springs
Struts
Rear LCAs
Rear sway (22mm, ITR)
Front sway (Both 24mm..so no need change)

Aside from the rotors/brakes, i have found very little info regarding front/rear upper strut tower bars and tie bars.

What does the GSR and ITR have stock in this respect? Essentially: lets set it straight. What needs to be upgraded on the GSR to bring the car as close to ITR specs as possible (excluding the brakes)?

 

the ITR frame has additional supports and welds. There's a trunk bar and i believe a slightly beefier subframe construction in the itr.

 

the itr has a thicker roof frame as well, you could seam weld up your chassis.

 

right. I'm talking about easily changeable parts.

 

The ITR has a rear strut bar, a tie bar, and a trunk bar. Those are all relatively bolt on parts.