Car is a 99 a4 1.8t Quattro has aftermarket t3t4 kit and front mount .if I turn the boost controller untill the external gate opens and a click back its ok . The previous owner unhooked the n75 . But as soon as it hits boost it bucks hard, any ideas ive been told I need a coil

 

I wish I could offer any suggestions. I'm just not all that familiar with the turbo flavored Audi's yet.