Just wanted to thank all that advised on the handling problems, especially dreracecar.
We had our first outing at the weekend and the car felt so much more stable than before.
We have uprated the front springs from 220lb per side to 500lb per side and stiffened the shocks. Also scaled the car and set at equal fronts + equal rears. Lauched at 2000rpm without brake, arrow straight. Arrow straight burnout, whereas before the car would tend to drift to the right. Not tried a higher launch RPM as yet due to insufficient runs and chasing a missfire.
Thanks guys