From the info I've been able to glean from various forums. The standard GTI and ED30 gti have some differences, although TT says not. The jury I guess is still out.
The only inklings of differences I can put my finger on is that there have been one or two standard GTI's in America with KO4 conversions that have either bent or broken a rod (Golf MKV forum). This is no definitive answer, as the standard GTI runs a slightly higher compression ratio which may have something to do with it as well, but just an observation!