stock downpipe expansion?

[03Powerstroker6.0]

MY truck my sig. on the stock downpipe under the truck theres about a foot of it thats an inch bigger the the rest like an expansion chamber or something, its all heat wrapped, so i cant tell, anyone know???

[smokeless]

My 03 had I believe it was called a resignator in the downpipe. It helps take out some of the drone and whistle the 03 turbo creates. I know when I removed my exhaust and put on aftermarket the whistle was crazy loud but you will get use to it.

[GregsSD]

That's correct. All it is for is to cut down on some of the whistle that the 03 turbos make.