The easiest way to tell a Porsche 911 Turbo from a 911 GT3 when they're running wild on a fast circuit like the Green Hell and on top of that, they're plastered in black camouflage, is to try to take a look at the exhaust pipes.
You see, the milder Turbo edition has two outlets on either side of the rear diffuser while the rougher GT3 sports two centrally mounted pipes.
Of course, there are other cosmetic differences between the two such as the bespoke aero components and wheels, but unless you're hammering the pause button more often than a kangaroo on trampoline, it's your best bet.
We'll remind you that the 991-series Turbo will feature a new 3.8-liter horizontally opposed six-cylinder engine with an advanced tri-turbocharging system and standard all-wheel drive, while the next GT3, a high revving, normally aspirated flat six driving the rear wheels, reportedly, exclusively via a PDK dual-clutch transmission.
Both of these models were filmed testing on the 'Ring a YouTube user. You can watch the clip for yourself right below the break.
Hat tip to Nicholas for the video find!