The car spotted at the infamous test track appears to be a Golf GTI Performance Pack with a range of changes such as 18-inch alloy wheels, red GTI-stamped brake calipers and lowered suspension, but the three-door also features a half-size roll cage, a more pronounced front lip spoiler and an enormous roof-top spoiler.
It is unclear whether Volkswagen is working on a model to bridge the gap between the Volkswagen Golf GTI - which has a 2.0-litre turbocharged four-cylinder with either 162kW or 169kW in performance guise - and the all-wheel-drive Golf R flagship, which has a maximum 221kW in global markets (206kW for Australia).
However, something more potent than the Golf R does not seem outlandish. Volkswagen has toyed with an even more focused and powerful version of the Golf, unveiling the Golf GTI Design Vision Concept at the Worthersee tuning show in Austria last year. That car was powered by a 3.0-litre twin-turbocharged V6 with 370kW and 560Nm.
Another possibility is that the car is a Club Sport version of the GTI, featuring a stripped-out interior and lighter body than the standard car, maybe that long-rumoured carbonfibre and aluminium-infused limited edition.
Whatever it is, this year's Worthersee tuning show in May could be where Volkswagen shows off this mystery model alongside the new Golf R wagon that was also spotted testing recently.
Click on the Photos tab for more images.