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Discussion Starter #1
I have a 2018 STI with Cobb DP and have noticed a hollow ringing noise during cold idle. It's most obvious when I 1st start the car and parked next to wall or other cars. I'm not sure if it's just because of the larger downpipe or a sign of a problem.

I thought it might be an exhaust leak since it seems to settle down after it warms up, but I have extensively inspected around downpipe connections at Turbo and Catback connections. I see no signs of an exhaust leak (carbon build up) and the noise is not any more noticeable when I get under the car.

Doesn't this sound familiar to anyone else. Driving me crazy wondering if there is a problem.

Thanks
 

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I have a 2017 STI with Cobb Turboback and do notice ringing/vibration over the whole car some days on cold starts lol ..

hilarious enough it set off a car alarm on a neighboring parked car from vibrations at idle on cold start LOL ... cobb tbe is pretty quiet too honestly (once it warms up that is :) haha)
 

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I've got a couple different noises from exhaust leak happening right now. One around the front O2 sensor that sounds like piston slap, and then my Tomei isn't sealing up properly. I confirmed all of these leaks with soapy water. Easy to test the cat back by just sticking a shop vac hose in the tail pipe with the vac's flow reversed.

At this point I really only trust soapy water to diagnose any air leaks: intake or exhaust side. For the manifold, I cold started the engine and immediately got underneath and sprayed soapy water on all gaskets. That makes it easier to spot air bubbles instead of sizzling water.
 

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Discussion Starter #4
Thanks for the response. I'm going to try and get a video or audio clip this afternoon, when I start her up to leave work.
 
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