are u sure that it wont cause any problems to the car if i go 4"?
Not at all. Your rubber intake tube is 4 inch if i'm not mistake. The only one catch I would add to this is that 4in tubing is slightly slower on throttle response but will get you the most top end power.
04 GP GT (1st car now my G-Ma's):
97 GP GT (GF's): "Project Pink Power"
00 VW GTI VR6 (15*V6): Slow and Low, That is the Tempo
91 VW GTI 8v: Big Plans