Porsche Tequipment offers a Manthey Performance Kit for the current 911 GT3 for even better performance on circuits. The 911 GT3 with Manthey Performance Kit lapped the Nürburgring's Nordschleife in 6:55.737 minutes. This is exactly 4.19 seconds faster than the 911 GT3 without kit.
Source: https://newsroom.porsche.com/e…g-nordschleife-28595.html