is it a genuine rs turbo box with lsd?u checked it?
mind the roads are very greasy this time of year,i can get my 306 d turbo to wheelspin in second with its beastly 90bhp(prob about 70 now as its 117k )
also the cars prob peakin in the 20psi range and as soon as it hits a certian rpm its gonna break traction you just need to learn how to feather it and control it when its on boost