I think Shimming the wastegate isnt worth it, You can get a mbc for about 10 bucks or u could make one your self, and it wont damage your wastegate spring. but its up to u, the shims go between the wastegate and the turbo houseing, where the wastegate bolts on(with 2 12mm bolts) u put them there. and how many depends on the thickness of ur shims. Do u have a boost gauge? If not u should get one before turning up the boost, so u dont over boost and hurt the motor.