Might be best to use short wire.
It may pick up emi.
That may distord your throttle response or it may distord your analogRead(), especially if there is no resistor at the end (causing your impedance to be 20 Mohm).
A voltage follower near the tap may prevent a lot of trouble...
On the other hand: car 'sensor' outputs often have low impedance (like wound wire tank sensors). So you might simply put a 100 ohm transistor at the end of the lead... if the sensor does not expect low impedance, this may damage the sensor...