just to add to that, as we know this subject is a
very common one, in the Video/Photo section of this
forum if you set it to look back for "all" posts or
whatever it is, you can find some video clips that I
linked to the page from trucks such as ours with a
couple diff types of mufflers, granted you will not
always know if they are the cat back or custom setups
but will also give you sometimes a better idea of how
it will sound, in fact i'll do better than that and
will place a couple links here for our trucks (again,
no idea whether or not they are cat back systems or
customs, but they do identify the muffler
generally

this first one is of a truck that got wrecked but
the guy thinks that his only mods on teh engine were
K&N intake and possibly a flowmaster muffler (you'll
have to ignore the music but you can still get a get
listen to what this truck sounds like, it's pretty
mean sounding and it's an N/A 3.3), actually 3 clips
of this guy's truck, i really liked the setup he had
on it too

v=ZmlHNUYcb4Y">http://www.youtube.com/watch?
v=ZmlHNUYcb4Y

v=4Me_VF4dsCM">http://www.youtube.com/watch?
v=4Me_VF4dsCM

v=1tCLnG_11So&mode=related&search">
http://www.youtube.com/watch?
v=1tCLnG_11So&mode=related& amp; amp;
amp;search=

3.3 with AEM intake and gibson exhaust

v=njkQpFP2gRI">http://www.youtube.com/watch?
v=njkQpFP2gRI

second, another flowmaster on a 01-04 (not sure
what year)

v=AweO8c7KShM">http://www.youtube.com/watch?
v=AweO8c7KShM

2005 frontier with bassani cat back (i'm assuming
it's a 4.0 but doesn't say)

v=9MlcdOPXKTI">http://www.youtube.com/watch?
v=9MlcdOPXKTI

v=JITsJFoiBAg&mode=related&search">
http://www.youtube.com/watch?
v=JITsJFoiBAg&mode=related& amp; amp;
amp;search=

2006 4.0L with what says is true dual

v=svcr58k_yKk&NR=1">http://www.youtube.com/watch?
v=svcr58k_yKk&NR=1

another late model with a flowmaster

v=WBI4m6ev5QQ&mode=related&search">
http://www.youtube.com/watch?
v=WBI4m6ev5QQ&mode=related& amp; amp;
amp;search=

this one says 2007 Frontier LE with K&N intake and
dual exit magnaflow

KUNk">http://www.youtube.com/watch?v=HNNBgN-KUNk

06 SE with JBA catback and spintech muffler (2
clips, one inside the cab)

v=KkmkPJdxYU8&mode=related&search">
http://www.youtube.com/watch?
v=KkmkPJdxYU8&mode=related& amp; amp;search=

v=5He52Z1Xu9g&mode=related&search">
http://www.youtube.com/watch?
v=5He52Z1Xu9g&mode=related& amp; amp;search=

spintech on a 2000 4 cyl fronty

v=nWsnP_ei6Ks">http://www.youtube.com/watch?
v=nWsnP_ei6Ks

hope that helps some