my catback makes a rattling / fartcan sound going from 1st to 2nd gear if im driving the car really hard.
it's not normal for this catback because i was on hondacivicforum and lots of members use the megan racing catack and they dont have this problem.

someone told me that it could be the hanger, and i always thought the hanger was the metal thing that is welded onto the muffler. but i just found out it's the black rubber thing, correct?
could those be causing this? and how?

 

I've heard of cat-backs hitting rear sway bars .... you might want to take a look at that.

 

that is a possiblity, also the hanger is "insulated" from the car by a little black rubber deal, if that has broken it could be causing the issue as well.

 

or maybe it could be bad hangers that are causing the catback to hit the rear sway bar?
someone also mentioned to me that the hangers for this catback are too short, could that cause the problem?