different muffler...
 

I have a 05 4.4 and I looked under the car and noticed that the muffler looks differnt that than the 01+, the 01 are a oval shaped muffler and mine is more bigger and is ribbed.. I think the newer models has an extra hanger also that hangs on the two rear air suspension...

I just fitted new 4.8 mufflers on my 2003 3.0D and they are indeed larger than on the pre-facelifted 4.6!However the hangers are a straight bolt on.