Porsche 996 911

The 996 moved the 911 to water cooling and shared its headlights with the Boxster, two decisions that kept values suppressed for two decades. The engine grew from 3.4 to 3.6 litres in 2002, when the front end was also revised.

The intermediate shaft (IMS) bearing is the question every buyer asks. It affects the standard Carrera engines, not the Mezger-engined GT3 and Turbo. A documented IMS replacement materially changes what a car is worth — and its absence is the single most common reason a cheap 996 is cheap.