Weird Metal to Metal Sound coming from under the hood

Hello, I have a 2008 Subaru WRX with 42000 Miles. SPT Exhaust, CTM Down Pipe. I noticed a metal to metal sound coming from the passenger side under the hood. It starts up when I start to hit 2300rpm on up. You can really hear it when you next to another car or barrier. The sound is like a spinning chattering noise that gets louder with acceleration. I was told by the dealer that it was an exhaust leak, so I replaced the down pipe gasket, down pipe to mid pipe, and muffler gasket. Still made the same Noise so I replaced the turbo to down pipe gasket again with a new one. Still so I replaces the mid. To down gasket again with another new one. Still making the noise, so went back to the dealer told them I replaced all the gasket twice, over a mo. Period. Then dealer said it was normal for the car to make that noise. So I got home and start taking all the heat shields off, the headers, up pipe and down pipe. The only on I couldn't get off was the top part of the up pipe it was welded on. Still making the noise, Checked Dip Stick, Diff Dip Stick, No Shaft Play in the Turbo, Hanger Bracket wear the Down Pipe and Mid Pipe connect. I Dont know Please Help!

Also it made the noise with the factory down pipe but it wasn't as loud as it is with the new DP