Three points, actually. The engine delivers a pleasing 198bhp, against 150 for the 2.0 Twin Spark. As a 1.6, it attracts lower road tax in some of the export markets its creator inhabits. This should apply here, too, as it will be registered with a regular 1.6's CO2 figures. And if you'd bought a 1.6 in the first place because you couldn't afford a 2.0, this is an alternative route to the extra urge you probably crave.

Its creator is Autodelta, a familiar name to those versed in Alfa Romeo things. The original Autodelta ran Alfa's works-backed racing teams a lifetime ago, and the name is resurrected (slightly cheekily, maybe) by Jano Djelalian's Acton-based, Alfa-specialist tuning company. Autodelta has produced J10 (Spyder/GTV), J11 (156) and now J12 (147) souped-up Alfas in recent times, the J standing for Jano. And, in best homologation-fantasy style, there are Evo versions. One such we sample here, gaining the Evo tag through an engine conversion one step beyond Autodelta's earlier efforts.

Part of what makes this a J12, not just a turbo conversion, is the bodykit (΂£1051.63 plus painting). Djelalian, a former interior designer, co-designs the kits under the banner of Autodelta CreativeDesign, and they are made, of glassfibre, in Oxfordshire. The nose section for the 147 is uncannily like that of the factory GTA, but that's just a result of convergent evolution; Autodelta designed it before the GTA broke cover.

Of main interest here, though, is the engine, a conversion available separately for ΂£4171. As well as that useful 198bhp at 6000rpm, there's 205lb ft of torque on offer at 4000rpm. The conversion's heart is a Garrett GT28 turbocharger mated to a stainless steel exhaust manifold, and blowing at up to 0.9bar boost through an intercooler mounted just ahead of the left front wheel. Controlling all this, unexpectedly, is a standard ECU. 'We reprogram it,' says Djelalian, 'and we are the only people who have managed to do so. Others use different ECUs and extra injectors.'

Machined piston crowns and combustion chambers drop the compression ratio to 8.9 to one, and that extra torque makes sensible a longer-legged fifth gear, as in the car here: ΂£293.75 fitted. All else is standard apart from an oil cooler, the engine's durability proven by unbroken turbo conversions dating back to 1997. Apart from a black intercooler pipe, the engine bay doesn't even look much different.

It sounds much different, though, thanks partly to the hefty pair of spaced-apart tailpipes that emerge, vee-engine-like, from the transverse silencer (another ΂£387.75, sorry). The sound is a smooth, metallic blare, indicative of unobstructed gaseous escape but not loud enough to annoy once the novelty's gone. That smoothness is more than just aural, too: this is an engine seemingly devoid of any mechanical reciprocation, its throttle acting as combined power rheostat and volume/pitch control.

Its connection is ultra-positive, too, delivering a deliciously blippable throttle response with none of the softness usual in old-generation turbo cars. Today's drive-by-wire throttles can be engineered in a turbo car to open more than the pedal dictates when off-boost, so delivering an extra rush of intake air which, once exhausted, can spin up the turbo more quickly.

So it's squirtable in traffic, with credible low-speed pull, no histrionics and excellent manners. But then the crank speed passes 3000rpm, the turbocharger goes from breeze to fast spin, and with a whoosh and a roar of high-velocity air the J12 compresses your frame into the seat as the g-force grows. Autodelta suggests 0-60mph in 6.7 seconds and a max of 135mph, both of which are credible, but it's the deep well of mid-range thrust that makes this 147 such an engaging drive. No naturally-aspirated 147 2.0 has lungs like this.

There are downsides. Throttle-off when boost is blooming, and there's a bit of driveline snatch. Try to use the torque in the wet, and it feels as if the clutch has let go: 'We've detuned the traction control,' says Djelalian, 'otherwise it would be intervening all the time.'

But we'll finish on an up. This is a car with real-world performance not massively far away from a GTA. And with its lighter nose it feels notably nimbler, even allowing for the test car's wide wheels and lower, stiffer suspension. Add up engine, exhaust, gearbox and a new 147 1.6, and you do bust a 2.0's price tag. The pay-off is a considerably more invigorating drive. Worth doing? Well, it convinced me.