Right the toe in is affected by the angle the hinge pins are at in the rear pivot block and the angle of the rear hub. The Original xx4 had a zero degree rear pivot block and 2 degree hubs (I think) So the toe in on the wheels was from the rear hubs. But on the worlds edition this was changed so the toe in was achieved by having angled hinge pins in the rear pivot block. To Change this you have two options..
With either option you will need one of these..
LOSA2112 Rear Pivot Block 0 Deg - £4.19 (From DMS Racing)
This will require the webbing being cut out so it looks like your original you will also need to drill out the screw holes to to remove the thread 3mm drill is about right but no bigger.
Ok So the first option is as follows to use the original xx4we parts which are as follows
Rear wishbones
LOSA9802 Rear Arms,Graphite XX4 - £12.69 (From DMS Racing)
Rear Hubs
LOSA2126 Rear Hub Set XX4WE - £6.49 (From DMS Racing)
The second option is to use the following losi parts which is what the team and alot of other xx4 drivers use. It slightly alters there suspension geomatery but it improves the car. They are also stronger and more importantly cheaper
Rear Wishbones
LOSA2132 REAR SUSPENSION ARMS,VLA XXXCR - £6.19 (From DMS Racing)
Rear Hub Carriers
LOSA2129 REAR HUBS, VLA XXXCR - £4.69 (From DMS Racing)
Hope this was helpful if you need any more help dont hesitate to ask.
A