We've been virtually alone in our criticism of the Focus RS. Other publications are heaping praise on its chiselled snout, eulogising over its competition-derived components and dribbling with glee at the way it attacks corners. We've driven several examples at great length, and none of us is convinced by the dynamics of the RS. Maybe we've all gone soft. Maybe rival manufacturers are intercepting each RS on its way to Evo Towers and sabotaging the Focus's sparkling chassis, although a number of chassis engineers we've spoken to (outside of Ford, obviously) harbour similar reservations about the RS, although a couple of them didn't put it quite so politely.

Whatever the truth is, we looked upon Superchips' invitation to try out its tweaked RS as an opportunity to drive a genuine customer car and at the same time sample the Buckingham-based electronics wizard's latest Ford-only power enhancer. Called the Bluefin, it's a hand-held device that allows you to overwrite the original Ford engine management program with an optimised program and then, if you so desire, re-install the standard mapping whenever you wish. Simply plug the Bluefin into your car's diagnostic port and the new program can be installed in about five minutes. In normally-aspirated Fords, the Bluefin liberates about 10 per cent more power and torque while turbodiesels can see improvements of up to 30 per cent. The cost of these benefits is ΂£499.

Now, when we've been wrestling with the RS Focus in the past I can't recall many rumblings about a lack of power. In fact, at 5.9sec to 60mph and a scorching 14.9sec to 100mph, the RS is the quickest front-wheel-drive car we've ever figured. The power delivery isn't to everyone's taste, though. Unlike most modern turbocharged engines, the Ford unit wears its forced-induction heart on its sleeve. Throttle response is a little soft and, just when you're wondering where all those horses are hiding, the turbo comes in with an almighty bang. Coupled with a stiff ride, limited wheel travel and a super-aggressive torque-sensing diff, the sudden rush of power can leave you fighting the car for overall control of your trajectory.

This hasn't stopped Superchips seeking out a few more wild horses. The Bluefin system gives the RS a claimed 237bhp at 5525rpm and 262lb ft torque (up from 212bhp and 229lb ft). The torque-limiting in first and second gears has also been relaxed - Superchips tried the RS with no torque limit at all in the lower gears and deemed it 'undriveable'. So the new program adds power and retains the spiky delivery that characterises the RS. Are you holding on tight?

You'll need to be because this is one angry car. The power boost isn't massive but it's just enough to give the engine a noticeably tougher edge. You'll have to wait until around 4000rpm for the fireworks to start and it's not until 5000rpm that the gruff four-cylinder motor is on full-charge and giving the front diff something serious to think about. The rabid top-end power tugs at the steering on all but the smoothest of roads, though it isn't really any more unruly than the standard RS. Bottom line: if you love the RS (and many of you do) then you'll love it even more once you've plugged in a Bluefin.

If there is a dynamic price to pay for the performance boost it's very subtle - just when the turbo is spinning up under light acceleration the steering has a very artificial weighting just around the straight-ahead. If you've ever played an old arcade driving game with simulated 'feel', this synthetic weighting will be very familiar. However, in the context of the more severe torque-steer and unforgiving ride that afflict the RS, it's hardly something that will ruin the experience.

The Bluefin system works brilliantly and is very simple in operation (I switched between the standard and enhanced program twice in as many hours). Moreover, a number of official Ford dealerships now stock the Bluefin and intend to sell it alongside Focuses and Mondeos, which suggests reliability won't be an issue.

Superchips have given the Focus RS even more of a performance edge, but that wasn't what the car really needed. Our feelings about the RS are unchanged. It looks fantastic and has all the right bells and whistles, but as a driver's car it is catastrophically flawed. If you live on a racetrack you'll doubtless have a ball in your RS, but for those of us who like to get our thrills on everyday back-roads with all their imperfections, the latest fast Ford isn't the hero we'd hoped. At least you can't say we didn't warn you.