I've got a '97 A4 2.8 12v quattro and I'm thinking about getting a custom dual cat-back exhaust installed. Anyone got a guess what I can expect to pay for that, roughly?

 

When you go custom then you have to factor in what your gonna put into it.
Dual muffler, single muffler, no muffler, resonators, straight pipe, tips?
Lets say for example a shop will make you a straight pipe at 2.5 inches from the cat back which will cost you somewhere around $200 parts and labor, but that will be loud!!!!
Factor in one resonator and a muffler of your choice and your're looking at roughly $600-$700, but you can choose what exhaust note you want and what flow, so do your homework here.

 

on mine i have a y pipe after the down pipes to single cat 3"in and out 3"pipe to a dual bullit muffler. sounds realy nice and deep. i bought the mufflers and piping 2 weeks used (to loud) for $250+200 install.then cat $70 plus custum ypipe and flex 200 install ypipe and cat last year and exhaust problike 4-5 years ago.