okay, I have never owned a car with a muffler as big as the one on my wifes TB. It also has what looks like a second muffler right before the tailpipe exit. I want to get a mild sounding magnaflow for it and dont know which muffler I should get and if I can remove (safely) the second "muffler" at the back of the truck.I figure if the muffler is that big then maybe there is some serious backpressure on these things and I need to be careful. I could be comletely way off base so someone please give opinions.

There are lots of options for a "performance" muffler. Take your pick.

The stock muffler is huge because people complain about hearing exhaust noise.
The second "muffler" is actaully just another muffler. Get rid of it too. It has a technical name, and at the moment I cannot think of it. But you don't need it. Its there to reduce the exhause noise even further.

Backpressure is not your friend, and no your truck is not designed to have backpressure. No vehicle is.
People are confusing backpressure with exhaust scavenging. Since your not looking into headers, your after cat exhaust system will not affect your engine performance much, except for some seat of the pants thrill.

2nd muffler is typically referred to as a Resonator.

By replacing the post-cat system, you really only change the sound of the exhaust, not the performance of the engine. Pretty much all of your backpressure is created in the exhaust manifolds, y-pipe, and catalytic converter as Hanr3 has already stated.

I posted a link awhile back that describes all of the theories of exhaust system design... I'll see if I can find it.

Maybe make that a sticky when you do find it?

http://www.blazerforum.com/fb.asp?m=17530

There ya go. I'll make a FAQ at some point that will include this. I'll also try to compile more info.

well, I basically just want to put an aftermarket muffler on it that will look better from behind and provide a little more sound and power. I just dont want to put anything on there that will decrease the power. So any suggestions would be helpful. Thanks.

Pretty much any aftermarket stainless steel muffler will look good. Sound is all personal preference, try Magnaflow, Gibson, Flowmaster for a stainless steel performance muffler. About the only gain you will get is a smile.