Almost a year ago to the day I was sat in this very same car, outside this very same workshop, on this very same industrial estate. But in those 12 months, things have changed. A lot.

Back in 2016 I was here at mountune HQ to jump behind the wheel of their M380-powered Mk3 Focus RS demo car, and while the car may still sport the same distinctive private plate, it is a totally different beast to the car I drove last autumn. For a start, it’s now black rather than Frozen White, thanks to a full 3M wrap from Joyce Designs. It’s also sitting lower to the ground on mountune’s Sport springs, while the same OZ Leggera HLT alloys now look a lot meaner up against the matte bodywork. Behind the wheels now live lightweight two-piece discs at the front, and mountune’s new performance brake pads all round too. But these are not the most notable changes since the last time I drive the car – nope, the reason I’m back here again is because the car has now been fitted with mountune’s latest – and to date, most powerful ­­­– performance upgrade package; the M400.

This builds on both the warranty-approved FPM375 and the M380 packages mountune also offer, so that the hardware upgrades now include a high-flow induction kit, uprated recirc valve, large capacity alloy intercooler, high-flow charge pipes, 3in downpipe with 200-cell sports cat, and a 3in cat-back exhaust system. These hardware changes mean the revised M400 software can run things that bit harder, resulting in an impressive 400PS (394bhp) and 560Nm (413lb.ft) kick up the backside. And, that… that’s enough to really bring the RS alive!

Like all of mountune’s upgrades the car has lost none of its everyday usability, and it’s hard to tell the M400 apart from even a standard RS when at cruising speeds and part throttle. Yes, the exhaust has a deeper growl to it – which, if you ask me is more than welcome anyway! – but it’s all very civilised and modern; the kind of thing you’d expect from a new car.

But the second you start to squeeze that pedal on the right the M400 starts to come alive! The throttle has a much greater sense of urgency when compared to the standard RS, the exhaust note sounds more aggressive (especially the pops and bangs when in Sport mode!), and that extra 60lb.ft of torque makes the M400 a completely different animal to the stock RS.

It’s more antagonistic, more assertive, more hostile than the standard RS. It’s harder-hitting than the FPM375. And it’s just plain more violent than the M380!

The Focus RS has been revered by all who’ve driven it, yet somehow tuned versions like this make the standard car feel fat and sluggish. It’s all very familiar, but like it’s been fed on a diet of nothing more than Red Bull and Smarties – it’s alert, awake, and keen to get going at any given opportunity!

This is immediately noticeable behind the wheel too. Get the RS out on the open road where you can really start to fling it about and you’ll notice that you actually need to drive the M400 slightly differently too! In places where the standard car would just hug an apex and pull itself around the corner without fuss, now, in the M400, there’s enough extra grunt being sent to the rear of the car to necessitate some driver input to correct things! OK, it’s not all of a sudden transformed into a rear-wheel drive drifter, but it definitely needs you to lift slightly, feather the throttle, or dial in a bit of opposite lock to keep things pointing in the right direction. It makes the driver feel a lot more involved in the experience – like you’re actually needed, and not like you’re a passenger in a computer-controlled point-and-squirt machine! For that reason alone, it’s worth the cash!

And when you do get going, it just keeps going. That’s the biggest difference between the M380 I drove last year and the M400, there’s more fun to be had higher up the rev range. It’s like the M380, but just more of it! More torque giving you a bigger shove in the back out of slow speed corners and around the country lanes, and more power at higher revs when you’re gunning it in a straight line! And more is always better, which is why the M400 is, in my opinion, the best upgrade mountune currently offer for the RS. Expect to see my own RS getting the M400 treatment any time soon…

Quick spec

M400 package, comprising; high-flow induction kit, uprated re-circulating valve, large-capacity alloy intercooler, high-flow charge pipe, 3in downpipe with 200-cell sports catalyst, 3in cat-back exhaust, mTune handset with M400 calibration, including exhaust optimisation, immobiliser, performance meter, custom gauge display, fault code reader; 400PS, 560Nm, Sport springs, high-performance brake pads, lightweight two-piece front discs, OZ Leggera HLT 9x19in alloys, prototype RS500 rear wing extension, 3M matte/metallic black wrap


£3495 + labour (from standard car)



01277 226666