When you buy wires and shrink flex for tuning your car, there are several factors you need to be aware of. First of all, you need to make sure that the wires are of high quality and can handle the required current without overheating or power loss. It is also important to choose wires that are resistant to heat, wear and corrosion to ensure reliability and longevity. When it comes to heat shrink, make sure it fits the wires properly to provide optimal insulation and protection. You must also take into account the car's specific wiring layout and the unique needs that your tuning process may bring.