There are times when the only thing you can do is admit you were wrong. I'm going to have to do this now, so sit back, tuck in to your popcorn and enjoy the show.In its original form, this article stated that the car pictured above was the first current-generation Focus we had tested with the 178bhp version of the 1.6-litre petrol turbo EcoBoost engine. No problem so far.I then wrote that I preferred this engine to the same unit in 148bhp form, "not so much because of the extra outright performance but because it's so much more flexible at very low engine speeds". Reader Andy Reeves responded to this on his Google+ page by pointing out (very politely, I should say) that this isn't true.And, what do you know, it isn't. I asked Ford for the power and torque graphs of both engines, and they are identical up to the point where the torque of the 148bhp one starts to fall away. The only reason the 178bhp one produces 178bhp is that the torque keeps going at the same level until nearly 5000rpm, a full 1000rpm higher than its less powerful equivalent.If you didn't follow much of that, all you need to know is that, at most speeds that you're likely to use on the road (except in very hard acceleration), both engines behave in exactly the same way. I honestly had the impression that the 178bhp one gave the Focus much better low-down performance, but it simply doesn't.This also explains why both this Focus and a 148bhp version I tested a few months ago produced very similar fuel economy of around 40mpg (not a bad figure, but not a great one, and some way short of the 47.1mpg achieved on the combined EU test). Driven in a similar manner, there is no reason why they wouldn't.My thanks to Andy for bringing this to my attention, and for demonstrating that reviewing cars isn't as exact a science as those of us who do it for a living sometimes like to think it is.The remainder of this review is exactly as it was when first published, starting with "The other thing which distinguishes ... "The other thing which distinguishes this Focus from others we've tested is that this one is in Zetec S trim. This includes such fripperies as LED tail lights and a leather-trimmed steering wheel, along with the more useful DAB radio (including Bluetooth connectivity, voice control and a USB slot), front foglights, comfortable sports-style seats and heated door mirrors, but I don't think I need to discuss them outside this paragraph.The Zetec S also has a body styling kit, which looks quite fetch, and 17" alloy wheels with moderately low-profile tyres, which I haven't experienced before. Focuses on 16s ride very well but look, shall we say, homely. Those on 18s look terrific but ride horribly. The 17s are a fine compromise. They're attractive, but the ride is hardly any less impressive than it is on a car fitted with 16s.The final point to make about the Zetec S is that it has what Ford calls sports suspension. Don't be misled. There is nothing sporty about it, and nobody who drives a Zetec S is likely to mistake it for a hot hatch, even if it looks a bit like one. It does handle well, though, and is both fun on twisty roads and comfortable on straighter ones.Poor visibility and a disappointing amount of room for rear passengers are the same in the Zetec S as for all other members of the Focus family. Engine 1596cc, 4 cylinders Power 178bhp Transmission 6-speed manual Fuel/CO2 47.1mpg / 139g/km Acceleration 0-62mph: 7.9 seconds Top speed 138mph Price From £20,495 Details correct at publication date