[Triflex]

Got the FBD exaust unit installed today. I was thinking I would hear more turbo whistle than I got but I can hear a soft whistle thru the exaust somewhat so I know it`s open. It`s kinda quiet in the cab although at times I can hear it a little. Is this normal w/ flowthru muffler? Would I get more whistle straight piped? I would think so. TIA . PS - My personal thanks to all you guys for your help in this install.