Need help diagnosing a problem.

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Here's the scoop. I had previously installed Stillen G3 intakes, and a stillen exhaust. the car ran great, but wasnt loud enough for me. I decided to increase the sound by going with Berk HFC's. I knew about the 'demon bolts' and decided to go straight to a shop for the install. Anyhow, as soon as I heard the car start up after the install, i thought to myself "this is NOT how this car is supposed to sound". I told the guy that installed them, and he assured me i'd be ok.

I did feel under the car to see if I could feel an exhaust leak, but I could only feel the warmth of the pipe, and no exhaust. You can hear in the video the car hisses at just below 2k rpms. I've heard other people say they get a huge power increase from Berk's HFCs but honestly I felt no change, or maybe even a drop.

Anyhow, I dont have anyone else with me to do isolation tests to figure it out, so I thought i'd take some video, and see if any of you with all your expertise could help me pinpoint what would cause this problem.

On to the videos.

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