Well that narrows it down 😂
What is it?
Not all cars are equal on performance so in real life they add restrictor plates in the intake to reduce power or add ballast to increase the weight of the car. Either/or will slow the car down. Being this is a game though, to balance out performance, some cars get a power increase and/or weight reduction to make them faster.
How to activate it?
Most of the time you won’t need to. If you go in to any online lobby then BoP on or off will be chosen for you.
If you do want to activate it though, once you’ve chosen a car and track and it’s loaded. On the screen where the background is a clip of car driving round the track. Click on the spanner icon at the bottom to open the set up page of the car. On the left, there is an icon labelled BoP, click it and turn BoP on.