I get this buzzing noise at about 2200-2800 RPMs. I know it's coming from my catalytic converter because i went under the car while someone revved my car up at that rpm range. My heat shield isn't loose and it sounds like its coming from the cat itself. So i dunno if my cat is bad or what. So, I'd appreciate ya'lls opinion on what it can be. I'm going to take my heat shield off the cat just to see if it is the problem or not. Thanks if you reply