Anti-Power Gear
From Stunts Wiki
Anti-Power Gear, or anti-PG for short, is a term proposed by Duplode to describe an effect which affect some Stunts cars. These cars, when subject to circumstances that would trigger powergear in PG cars, such as driving through ramps and loops, suffer deceleration instead of shooting to top speed as a PG car would. Depending on the car characteristics, the effect can be strong enough to bring the car to a standstill. By far the most remarkable example of an anti-PG car is Lamborghini Countach, its handling technique being strongly influenced by it. Above 200mph, the Speedgate XSD is affected by anti-PG as well, albeit in a much milder form.