How does McEwen using a fake EXR guarantee Garriga will win the race?

Garriga hired Nicky to pose as a disgruntled ex-employee and sell a fake version of his EXR to McEwen, his biggest competitor. What I can't figure out is how does McEwen using a fake EXR guarantee that Garriga will win? Is the fake EXR supposed to make McEwen's car slower? Because if the EXR Nicky sells McEwen is just fake and doesn't affect the car's performance how does Garriga think that guarantees he'll win? Unless Garriga thinks that once McEwen thinks he has a legit EXR he will stop trying to find a way to get a leg up on Garriga. Maybe I'm missing an element to the con? Any thoughts or explanations would be greatly appreciated!