You do know dirty air is a thing right?
And you don’t know difficulty setting does not affect their car performance, only how they perform in/out of corners?
This is not an full arcade racer, where a boost button will instantly make you faster than others, they have the same tool as you, and are preprogrammed to be using them in near optimal fashion on each session of a track, so players will have to up their game to match them.
I know this is hard to swallow, but the more I played in both single player and multiplayer, the more I realized how little most people actually knows how to optimize the tools and mechanics that were given to them.
You don’t just brake, turn and accelerate in this game, there’re a lot more things you need to manage