Intake restriction to earn more money?

[NORKETT7]

On the top left sometimes when in City driving one i get something like ( Add intake restriction to earn more money)

I would like to know how to do this?
I hope you know what i mean.

Thanks

[Barney [CA]]

in garage(shift+p). it gets saved in the current setup.

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€: 50% earns you 50% more. so a +4 car can get up to+6 (4*1,5).
+2 cars would get you 2*1,5=+3

[NORKETT7]

Thanks pal