my boy told that it is illegal is that true?

 

depends what state your in. In NH its illegal to change you exhaust in anyway that makes it louder. Are you running a turbo? If not forget 3 inch piping.

 

different states have different laws... in delaware as long as it meeds db levels and has emission implememts still installed it is ok. and it helps turbo's immensely. 3" with apex-i n1. nice sound too...as for emissions implements? im not at liberty to say.