Sub-four-second 0-60s and 600bhp are performance figures that were once exclusively the domain of supercars, but not these days… In the first installment of Stig’s Garage, we take two of the fastest SUVs on the market and pit them against each other on the Top Gear Test Track. Which one will top the leaderboard, the 631bhp Porsche Cayenne Turbo GT or the 590bhp Audi RS Q8? Join The Stig and Becky Evans to find out.