Mitsubishi has had a tremendous amount of time to develop this car. The Evo IX is the last of a line which stretches back almost unbroken to the Evo IV, and there have been far more reworkings than that numbering system would suggest. The Evo IX MR FQ-360 brings the run to an end (the Evo X will be based on a different car), but is it also the ultimate model?It's certainly the most powerful, if you don't count the rare and reportedly fragile 400bhp limited edition of a couple of years back. This latest development of the now twenty-year old two-litre turbo engine produces 366bhp (as ever, Mitsubishi is being modest with the number in the car's title), but any suggestion that this makes it too hot for normal road use can be laid to rest right now.In fact, one of the truly remarkable things about the FQ-360 - and there are several - is just how tractable it is. It was the FQ-340 (see road test) that was the difficult one, doing nothing much to speak of below 3500rpm and then letting rip in no uncertain manner. The 360 is awake by 3000rpm, and while this wouldn't be significant on a track day it makes a big difference on the road.Once the turbo has come in, the 360 becomes a monster. There's something about the way this four-door saloon (albeit a dramatic-looking one thanks to all the competition-derived add-ons) erupts towards the horizon that brings a big smile to your face even though you know you should really be tut-tutting about the waste and irrelevance of it all.But it doesn't have to feel wasteful and irrelevant. Below 3000rpm the 360 seems quite happy to potter around town in a way that the 340 wasn't. The older car snarled and complained at sensible road speeds, and always felt like it wanted to go much faster. The 360 is much more peaceful when you're not pushing it, as if it's more confident in its abilities and is happy to wait for the right moment to display them.The 360 is a better road car in other ways, too. It's pretty loud, thanks to that immense exhaust tailpipe, but I don't think the interior noise levels are quite as pain-inducing as they used to be. And the ride is that little bit more friendly - run over a manhole cover and you might sigh with frustration, wishing you hadn't done that, but you won't wince in discomfort as you might have done in the past.This could be bad news. Better ride quality? Has the Evo gone soft? Well, the suspension has, but the concept hasn't. For all the talk of acceleration figures - and this is a car with a quoted 0-62mph time of under four seconds - an Evo is nothing if it isn't a wondrous thing to drive.The 340 was certainly that, but it could be a fractious beast. Tiny alterations in throttle opening could have a significant effect on weight transfer across the chassis, and although this kind of adjustability is what you want in a competition car the behaviour was too sharp, too demanding for road driving.If I had to choose one thing that I would have wanted to be improved on that car, this would have been it, and now the job has been done. The chassis is still responsive to small changes in throttle position, and I have no doubt that on a race circuit you could still make the 360 dance every bit as much as you could the 340. The important consideration is that with this car you can also drive home again in a relatively relaxed manner.There is plenty to be sniffy about in the latest Evo. Like the earlier cars, it has a Dullsville interior, and the huge rear wing does its best to foil any attempt at seeing what's behind you. It's also difficult to make a case nowadays for a car which can't beat 20mpg on the combined fuel economy cycle (during which its performance potential is left untouched) when so many SUVs can do better than that.But in supersaloon terms, the FQ-360 is a wonder. Its straightline performance is awe-inspiring, but it's the way the car deals with its power that is so impressive. Mitsubishi will be doing well to match this painstakingly developed car with the Evo X, which will use a different engine and be based on a different floorpan - but that's the company's problem and not ours. For sporting drivers, the significance of the FQ-360 is that it is indeed the ultimate in an astoundingly capable line of cars. Engine 1997cc, 4 cylinders Power 366bhp Transmission 6-speed manual Fuel/CO2 19.6mpg / 334g/km Acceleration 0-62mph: 3.9 seconds Top speed 157mph Price £34,539 Details correct at publication date