Good: differential changes it completely, costs less to upgrade than a fancy satnav system.

Not so good: we had to give it back.

Back in July last year the CompleteCar.ie team attended the Irish launch of the new Volkswagen Golf GTI and having put the car through its paces on some of our favourite test routes in the world the first question we had for the nice PR man was "When does the Performance Pack arrive?"

This had nothing (or very little at least) with us wanting a faster car. Instead we felt that we had discovered the limitations of the car's XDS 'electronic differential' system. When we drove the standard Golf at its original launch we were amazed with the affect the XDS system (previously the preserve of GTI models) had on the handling characteristics of the car. Gone was the understeer that had so blighted previous versions of the Golf to be replaced with a balanced, composed drive with little or no drama. That may sound dull, but while driving enthusiastically balance and composure are infinitely preferable to understeer that just wants to drag you towards the outside of every corner and ends up with you backing off, leaving a disjointed driving experience.

Unfortunately that feeling returned when we first began to attack corners in the GTI. Despite packing an even more advanced version of the XDS system than the standard car the GTI just possesses too much power for the electronics to rein in in a satisfactory way. Sure, you could still have fun in the GTI, but that disjointed feeling returned to blight the experience, which is why we were so interested in the Performance Pack.

Tick the box for this option and the engineers in Wolfsburg will release another 10hp from the 2.0-litre turbocharged engine, bringing the total to 230hp; replace the standard GTI's 310mm brakes with 340mm units and fit an electronically controlled front differential lock. It is not, as some have suggested, a mechanical limited slip differential like that fitted to the Renaultsport Mégane, but instead features a pump that closes a multi-plate clutch via hydraulic pressure, limiting the amount of slip at individual wheels.

And it is this that transforms the Performance Pack GTI - not the extra power. If anyone tells you they can feel the difference between the 220hp car and the 230hp one in a straight line check to see if their nose is growing, as, with the added weight of the bigger brakes and differential, the Performance Pack car is only a tenth of a second quicker to 100km/h. No, it is through the corners that the clever differential begins to pay its way, aided by those bigger brakes.

A small motoring show on BBC2 recently tested the Performance Pack GTI and its host described the differential as 'physics defying'. Without meaning to get that deep into hyperbole the car is sensational - pitch it into a corner at speeds the regular GTI would wash out on and you can feel power being shuffled to the outside wheel, allowing it to hug the inside of the corner and pulling you through the bend. What is even more impressive was that during our time with the car the roads were at best described as greasy, yet this did not faze the car one bit. Sure the traction control kicked in once you hit the 2,500rpm sweet spot in lower gears, but once beyond this it was unfussed, composed and hugely exploitable.

As the differential system is electronically controlled its 'brain' is constantly monitoring the position of the accelerator and steering and can, if needed, send up to 100 per cent of power to an individual wheel. Other than bouncing over kerbs on a race track, the biggest use for this is when the grip levels underneath vary across the axle.

Then there are the brakes; while you cannot truly tell the difference between 220- and 230hp you can most certainly tell the difference between 310- and 340mm. There is just so much stopping power from the upgraded system that you feel the confidence to lean on them more than usual, braking harder and later than ever on a fun piece of road, secure in the knowledge that the brakes will shave off excess speed before the differential pulls you through the corner. They are an enticing combination and worthy of the entry price alone.

Which brings us to the car itself. As standard the Golf GTI costs €35,500 for the more popular five-door version (three-door costs €34,545). The Performance Pack Golf in the same five-door body style costs a mere €36,810 - or €1,310 more. The Discover Pro infotainment system with eight-inch screen, USB and two SD card slots costs €1,639, or you could spec 18-inch 'Austin' alloy wheels and tinted rear windows for €1,300. If you love driving, don't do any of that; get the basic GTI, spec the Performance Pack and you will have all the car you need and the best GTI that money can buy.