I put a straight 5" exhaust on my LB7. Didn't whistle much more than before.

It could be an aftermarket turbo.

 

I was wondering why I could hardly hear my turbo on my 01 duramax, I guess it's pretty normal for a stock rig.

I would wonder if the guy has a different turbo. I have a 93 GMC Typhoon and the stock turbo whines like my wife It's loud inside the car. I've never heard of changing the intake that results in increased turbo whistle...maybe I'll try that too

 

The IHI turbos on the LB7s are QUIET!

 

Yea, the point I neglecte to make is that I've had 3 different turbos for my Typhoon. All 3 have different sounds. GT35R sounds like a wind tunnel with little wistle, 20g stock upgrade has a different sound than the stock. It's all good, love my Duramax

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intake works the best for the whistle or bigger turbo

 

I have an 02 duramax with just a muffler delete inside the truck the turbo is pretty loud between 6-12 lbs boost