SVD plate etc, or something on the chassis, google search will prolly reveal the answers, as i don't have them all
there are differences, e.g power output. GTS-R's put out something like 300hp, if not a little more
they came with a large FMIC, upgraded turbo, ECU, exhaust, better boost, limited edition BBS rims etc.
The whole GTS-x/GTS-R thing is like the GTS-t/GT-R thing, allot of people tried to copy them, and some people got ripped, cept the GTS-x/GTS-R thing was much, well, smaller/less popular.