its fairly straight forward as far as im aware and the parts needed have already been listed...the only complication for this conversion is the management but thats solved by running aftermarket management
a few people that i know have done the conversion without problems...
a mate of mine has a Mk2 Golf Rallye with a 20v turbo running 319hp and 361ft/ibs torque, running M3 injectors, standard turbo, steel bottom end, Motec engine management, and a quaife 6 speed gearbox...linked up to the standard Rallye 4x4 system...quick is an understatement! He wants to run the S3 4x4 gear in there and change the turbo for more power at some point
bassboy