Maybe you could try Darrenīs front mod as seen on page two and three here:
http://www.oople.com/forums/showthre...t=90035&page=2
Itīs made for mid motor but obviously to have less steering coming out of a turn so maybe could work for you, too. The little trimming and "stretched" standard length turnbuckles just to test it should give you an impression if itīs any good without having to buy longer ones for racing.
Besides that and setup/ tyres I would doublecheck the diff just to make sure it isnīt responsible for the undesired cornering.