It's not the heatshields, but the welds inside of that a-pipe that have caused the inner pipe to become loose and vibrate against the outer pipe. Evidently he's had luck putting screws in it. I guess the screws help secure the inner pipe that is loose and stop the buzzing. I doubt this is a sure fix, but I might give it a shot anyways. I read of another guy on here having holes burned in his a-pipe and then welding down in those holes to secure the inner pipe. He said it worked and he hadn't heard the buzz in a long time. This was an old post. I think I'll go to an exhaust shop and see what they think about these options. If they don't work I'll live with the buzz or buy a new header. Forget the $500 for the oem a-pipe.