As petrolheads eagerly await the arrival of the 345-horsepower, all-wheel drive Ford Focus RS, its milder sibling is getting a little upgrade. It's not uncommon for drivers to upgrade their cars with performance parts, but it's rare for those upgrades to come with a factory warranty.

The 2015 Ford Focus ST is one of the exceptions. It's getting a new "mountune upgrade kit" that boosts output from the 2.0-liter turbocharged four-cylinder engine to 275 horsepower and 296 pound-feet of torque. Those are increases of 23 horsepower and 26 lb-ft. Granted, the car needs to run 93-octane fuel to get the full benefit.

Most of the gains come courtesy of a performance ECU, which Ford says has more aggressive mapping, and allows for quicker throttle response without impacting durability. The upgrade kit also includes a high-flow intercooler, mTune handset, and a new air-induction system.

The kit is priced at $1,900, and is available through the Ford Performance website. Ford says it is legal in all 50 states, and maintains the factory new-car warranty when installed by an authorized dealer.

This isn't Ford's first foray into factory tuning. The Blue Oval previously offered a performance exhaust system for the Focus ST, plus a ProCal handset for the Focus and Fiesta ST models that could fiddle with a car's onboard software by plugging into the diagnostic port under the dashboard.

Like the rest of the 2015 Focus lineup, the ST got a handful of upgrades as part of a mid-cycle refresh. The sporty Focus now boasts a redesigned center stack and center console, a flat-bottomed steering wheel, and some tweaks to the exterior styling and suspension tuning.

Soon, though, the ST will go from being the sportiest Focus model available, to being the more practical and affordable alternative to the bonkers RS. This will be the first time the RS is offered in the U.S., as it was previously a Europe-only proposition.

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Ford's mini muscle car