Detailed spec of the Xrs is now online, you don't get the items below, but you still get a lot for the money i think. The only parts you would really need are the one way and diff balls from perhaps Acer 1/8 & 2mm.
One way
Ceramic diff and thurst balls
Moulded rather than alloy rocker cranks
Steel not ti-nitride shock shafts
Moulded rather than alloy steering arms
http://ttechracing.com/htmlpages/xrsspecification.html