If I swap a stock exhaust for a 4 inch MRBP turbo back exhaust....will I get the cool turbo whistle? What is the different between doing this and doing this PLUS adding the muffler delete pipe (i.e. deleting muffler)? Is the turbor whistle I've heard on some trucks the result of the larger exhaust alone of the result of no muffler or some other modification?

 

There is a difference between the compressor "whistle" when under power, the high pitched one, and the turbine whine/flutter sound out of the exhaust. The 7.3s have a distinct different sound than the 6.0's do, you may have heard a 6.0 and wondered what the F it was coming, sounding like a fighter jet. Simply straight piping (removing the muffler) the stock exhaust will get you that cool exhaust whistle, however making the exhaust larger (4-5") will make the sound deeper/throatier, and also help lower your exhaust temperatures.

 

My truck sounds just like this:
http://guzzle.rbmicro.com/mp3/City.mp3

Now, I actually hear a lot more whistle than you hear on the clip, but this is focusing on the exhaust sound. Our trucks whistle from the intake side. I have the 4" SS MBRP, WW, Foil Delete, and 6637 filter. Without a turbo change, those mods will give you probably the most whistle from the 7.3s. It's enough for me, but others want whistle like this:
http://video.FTEs diesel forums.com/...3bb0950534.htm

As far as I know, the only way to get that is from a 6.0.

Joe