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Hey all,

I have this whining noise when I’m in boost with moderate to WOT. Only mods I have are green filter with air box cover removed. I first noticed it was after I put on the green filter which was a few thousand miles ago. I took it to the dealership who blamed the green filter because it was “loose”. Today I decided to try it with no filter on and the sound is still there. Do I have a boost leak or is this normal? Car is 2016 focus st1 with about 20k miles. Here’s a short video of the noise.

https://youtu.be/-twxZHprmSk
 

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That does not sound like the normal turbo noise to me... When I put on my new charge pipes, I had a very similar sound only under half to full boost but the AP showed I was still getting full boost (23+ psi) turns out a had a slightly loose t-bolt clamp. I'd check all the clamps and make sure they are all tight.

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Yeah my ST definitely doesn't sound like that. Sounds similar to super charger whine. I don't think it's boost leak because that sounds more like a hissing or air rushing sound. I would pressure the dealership to check it further. IIRC there was a user a while back who had their turbo completely fail and the dealership blamed it on a loose aftermarket filter saying that dust got into the turbo and damaged it. Hope that's not the case here.
 
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