Try fitting the front sway bar rather than the rear, having less rear roll will make your tyres work harder, and we already know the M-Grips are pretty rubbish on carpet. Fitting the rear sway bar will probably increase your oversteer issues rather than solving it.
Also try softening the rear suspension by moving the top of the shocks inboard (not sure if this is possible, been a while since I had my M05).
I had typed a nice explanation of the sway bar and pitchinging/rolling but then my internet connection dropped out!
