Hi, I have a kawasaki ninja 300 and I live in NJ. I was wondering if I would get ticketed for having a straight pipe?

If they have a noise ordinance you may. NJ is pretty tough on those things, I lived there 35 years and had issues with my Porsche and TR3 on exhaust noise during inspection .

Yeah.. you would, in a hurry... there are very very few places you could get away with it. Besides... it sounds horrible without a muffler. THe only ones that sound good unmuffled are old Harleys and old Indian twins.