3.4-litre six-cylinder engines currently used by the Boxster S (232kW/360Nm) and Cayman S (239kW/370Nm) flagships.
The more powerful GTS duo, which were first discussed by chief Porsche 991 engineer Andreas Preuninger at the 2013 Geneva motor show in March, will improve upon the respective 5.1sec and 5.0sec 0-100km/h times of the Boxster S and Cayman S, likely putting both models into sub-5.0sec territory for the first time.
Still under development, the images reveal both GTS models will receive a new front bumper with revised intakes and, in the case of the Cayman, new LED daytime running lights.
At the rear, a slightly taller wing joins a more aggressive diffuser.
According to information reportedly leaked from a US dealer meeting in October, standard equipment will include a manual transmission, Porsche Active Suspension Management (PASM), a new steering wheel, upgraded leather upholstery and 20-inch alloy wheels – although our photographer says the two test cars were wearing 19-inch alloys wrapped in winter tyres.
A dual-clutch PDK automatic transmission will be optional, while a package boosting power by roughly 11kW has also been rumoured.
An April premiere at the Beijing motor show has been rumoured for the GTS twins.
Click on the Photos tab for more images.