no modification needed to the airbag wiring, the original wire of airbag is long enough.
here my story:
because i am very tall 6'2", usually i bend my knee more than others during normal driving, that has no problem at all.
i went to the ipoh small track 2 months back, i found out that i could not do "heel and toe", that was because i bent my knee too much during driving. And if i tried to do "heel and toe" i would have to twist my whole body, instead of twisting the right leg only.
to less bend my knee, i need to move my seat towards rear, but then the steering wheel is too far from me. so i manage to customize spacer and extend the steering wheel closer to the driver.
it is now possible for me to do "heel and toe" in this setup, i still need more practice to get used to it.