Addam,
Some things to try (all will give improved on-power steering):
*Run a one-way or spool up front (if you aren't already).
*2 degree caster blocks - but you'll lose some high speed turn-in, and the car will be more twitchy at low speeds.
*thicker rear roll-bar (or thinner front)
*straighten up the rear shocks (ie: more vertical)
*stiffer rear springs
