It's only worth it if you drive the car hard to be honest, normal day to day driving will feel the same! I would only recommend the haldex performance controller on cars no longer running standard power, and has uprated suspension mods to make use of the extra traction it provides.
It was from awesome and it was a staggering £779.70 and yes it was a forced purchased had code 65536 I know it's a lot of money but I'm loving it smiles all round ever time I go out driving down the small lanes round me. Right the tuned controller runs at 1375(NM) and the standard controller runs at 625(NM) well that's what the bits of paper in the box tell me. I ordered it fro
Awesome but it came from the TT shop but when I was phoning round for prices didn't find the TT shop that helpful they where ment to phone me back in an hour but 2 days later they did lost sale.
It is an upgrade, the standard mk1 haldex controller is prety dim whitted and sluggish, the upgrade is meant to solve this with faster reaction times and more proactive transfer of power. Can spend the same amount on suspension setup...it all helps.