[Shaved &/or Laid]

for some reason, it seems liek i have ****ed up my exhaust terribly. it rattles troughout hte hwole powerband following hte swap. I dont understand, i even had my HUGE dad tighten my exhaust bolts ultra tight on the cat. What else could it be ? i basically unhooked a lot to get to the shift linkage, and didnt put all the hookups to the car back on. that my problem ? also, would a bent heat shield do that ? it sounds like its falling off.