b44 poor handling

[m1buc]

i have had my b44 for a few months. and run it with no problem, but recently have had a problem with it now wanting to spin the back end out. every time you come out of a corner and put the power on. i have stripped the car down twice. but can not find a problem, i have rebuilt both diffs with new parts. tried all different set ups and tyres. but these only mask the real problem.
has any one had this problem before? or know how to fix it? i am all out of idea's.........