Ok, I am trying to find a good exhaust system.  I have the tail pipe part now I'm going for the peice that comes off the headers.  Looking through the magazine I've seen different prices varying from 100-200 to 300-400 dollars.  The more expensive all seem to have the cat-back system.  Now for the stupid part of the question.  What is the cat-back system and why so much more.  Thanks for the help.

the catback is the part that has the mufflers in with it that explains the higher prices

the piece that connects to the headers is the mid-pipe or cross over pipe whichever u like 2 call it, it contains the cats,

if your looking for crossover pipes skys the limit, a matter of emissions comes into play, high flow cats or off road pipe (x or h, whichever u prefer) all depends on where you live

catbacks are a matter of personal taster, stock sounding, louder than stock, loud and really effing loud.  flowmaster force II sounds good but is mild mannered and decnetly quite for cruising, flowmaster american thunder nice and barky, only 2 ive heard so its really up to you.

If I could suggest something, get a set of flow tubes, tail pipes and then some Flowmaster Super 40 mufflers and not the usual 2 chamber Flows.  These don't sound like every other Mustang on the planet and give more power.  I changed from the Dynomax Super Turbo and could tell a difference right away.  They do have that distinctive Flowmaster sound, but yet still different.   

Thanks guys  

Greetings I have a 00'GT which i have installed a Mac Cat back system on i found it on E-bay for $313.00 buy it now (that price included shipping!!!)  I had this same system on my previous 02'.  The Mac system was a 2.5" with stainless 3" tips.  Great price and even greater sound.  30 minute install!!!  

That wouldn't fit on an 89 LX would it?