The car is an 01 A6 Quat. with a 4.2 The problem is a check engine light with a fault code for a cat gone bad. I live in an emissions testing area, so with that info I need some advice about options to replace my bad cats. OEM is $1500. Not real keen on that.
What would you do with this car?
I would like a little more Ooomph out of the 4.2 and wouldn't mind a little more growl out the pipes.
Options or ideas?

 

I have my stock cats if you would like to use them. The issue with the high flow is you never know if you will still be able to pass emissions and over time the aftermarket cats tend to clog

 

I WOULD UPGRADE THE CATS, WON'T CHANGE ANYTHING FOR SOUND BUT IT HAS BETTER FLOW. EMISSION WISE, IT ALL DEPENDS ON WHERE YOU LIVE AT. IF YOU DON'T NEED TO PASS THIS, I SAY ALL THE BETTER TO UPGRADE

 

Hi-Flow cats work great, eliminating cats even works well. Just need to be aware of your emissions laws. Generally these cars have 4 cats, 2 per side. The front cat can be eliminated and still pass emissions (I did it here, although with a 2.7T). I would think replacing them with high flow would keep everything in check but relieve a little back pressure and work real nice on your 4.2. If you want to spend some money, they also make piggie pipes for the 4.2 now. Check vasts web site for more: www.vastperformance.com Those include high flow cats and will free up some grunt.