well for one, the GSR kit will fit on the ITR but you'll have to get a different turbo exhaust manifold to fit a B16/B18C5 cause the gsr manifold won't fit on the GSR head.. Other than that, the entire kit will work with the ITR. Compression on the R is a little higher on the R than GSR though boost would work just fine on it if you keep the boost relatively down 6-8 psi, If you're planning on going higher in boost levels, I'd put in some 9:1 CR pistons and a H-beam rod of your choice and you should be fine. If more block streigth is in need, obviously sleeving the block is you absolute best thing you can do... Though, if you plan to sleeve the block, I'd hold off on buying the pistons at this point, run lower boost (6psi) and sleeve the block to 84mm and run a bigger 84mm piston to up displacement equaling in more power...