Put on my greddy evo2 cat back yesterday and I can rev it a lil (not past 3000) and itll rev, then have a little after rattle. When I drive it does the same but if I rev it a ton while sitting itll rattle at the same time. Inside the car it's super loud. Know what it could be rubbin on or is something inside the muffler? already took cat heatshield off from rattles awhile back. and it didnt rattle like this when I had on my stock exhaust.