I had to have my gearbox rebuilt, so while they were in there, I had a Quaife automatic torque biasing (ATB) helical gear limited slip differential (LSD) fitted.
http://www.quaife.co.uk/differentialsThe results are unbelievable - this does what a FWD should do - literally drags me around the corners! I'll need to get it onto a Race Track to find the limits - I can't (safely) on the road anymore!
Forget the bulkhead/clamp/arb/subfame upgrades - they made an insignificant improvement compared to the LSD, although I expect they add to the accuracy of steering now required.
Only issue is having to wind the car back out after the corner, as it loses self-centering under power. (sort of benign torque steer)
It's starting to feel like my 9000 used to (apart from the power).
Oh, and did I mention the Hybrid turbo, uprated ECU mapping, sports exhaust, lowered & uprated suspension and wider wheels?
My car ownership principle is simple, every time something fails, replace it with something better

Antony.