Only so much

For a commercially available passenger vehicle, there is only so much one can do to improve its performance in ways allowed by the relevant authorities .....

Air filter? Check
Air intake? Check
Strut arms? Check
Grounding wires? Check
Lighter wheels? Check
Better tyres? Check
Suspension? Check
Brake lines? Check
Engine flash? KIV
Big brakes? On the way.....

Errr what else?

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