Sounds like a boost leak

[Lostfarmboy]

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.

[Chamberpains]

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.

[Lostfarmboy]

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