I have a 4040XL. It's got a good throaty idle and sounds good when you open er up. I got the XL because I had some droan issures with my previous muffler and it virturally eliminated the droan. It also is a little longer and fit really nice where my other muffler was.
I personally wouldn't buy another muffler for a diesel that wasn't an Areoturbine!
Not everybody will anny up and buy one. Most people on here probably don't have any muffler at all. User CSIPSD has one and likes it. He will probably see this soon and reply.
The muffler that I had was a straight thru 4" with a bunch of louvers around the inside of it. It had no packing or anything inside it. The muffler was installed so that the exhaust would flow up and over louvers (they wouldn't "catch" the air). I originally just took off the muffler and tailpipe trying to figure out the droan and noticed a big EGT difference. I then put the Areoturbine and tailpipe back on and the EGT stayed exactly the same as no muffler.
A little added FYI my truck has a 3" downpipe because that is all the bigger that will fit in an OBS. So I was really suprised when the "straight thru" 4" muffler made more restriction than a 3" DP.
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