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My demandated 871 sounds like it has a boost leak but the noise is coming out the exhaust. I don't understand what could cause this. Any ideas would be helpful. Performance and fuel mileage don't seem to have changed any.

Did you hollow everything out properly when you demandated it? There should be nothing but empty cans attached to your truck. Anything left inside them will cause soot build-up and exhaust restrictions.

I left about 1 inch all the way around the outside everything else is gone