F430 feels twitchy under braking

I'd look for:

1) Worn brake discs/pads
2) Worn Tires
3) Poor Alignment

If there's something wrong with the Alignment, it may mean that there's some bushings, or suspension components that are worn.

Could also be a poor alignment causing worn tires, causing it to track weirdly.

Worn brake discs/pads...are also a possibility. Should be either of these 3 things in my opinion.

 

I doubt its going to be too hard to resolve this.

Uneven braking as described is very likely to be related to both braking and geometry. The F430 (and also 360) has Bosch EDB, electronic brake force distribution so tries to compensate to keep braking stable under heavy sustained emergency braking by adjusting amount of fluid required to brake individual wheels via use of valves however if one of the wheels is over compensating more that the parameters in works within then it won't be able to prevent it.

Typical things are siezed pistons in the brake caliper or uneven wear on the pad surface can even cause it. Siezed pistons in caliper can happen from being stood up and not used, they can rust so they don't move freely. You can try cleaning the caliper and pistons up or if they are pitted (damaged by corrosion) buy replacement Hills Engineering pistons and rubber seals for quite a few Ferrari applications rather than replacing the entire caliper (expensive in comparison to changing a small circular piston).

Also on geometry if the car hit a curb (even low speed) it can be enough to put the geometry out so the wheels are pointing in the wrong direction and try to follow that. A simple geo check and verify if this is the case.

I've even seen cases where tires cause this in the past (again from uneven wear).