I own a 93 Z28 A4 (Stock except for ECU and Cold Air) that has a bad rattle in the catalytic converter. I took it to the shop and was told that it was bad, and that part of the material inside had probably busted loose and was rattling around. He said it would be $600 parts and labor for a replacement (either Magnaflow or Dynatech, not sure now) one. I don't really want to, nor have the money to, replace the catalytic converter for as much as it will cost. My dad has told me about the device called the test pipe. I asked my shop guy and he said it is a federal crime, but can and has been done a lot. My question is, how will a test pipe effect my car? Specifically, will any check engine lights come on? Will it cause the air/fuel mixture to change? Will it change the sound of the exhaust, even though I have stock mufflers? Has anyone had experiences with them? Thanks for your help, guys.

 

cut that damn thing off and put in a test pipe many people run without cats including me

 

That price sounds a little outrageous. Have you tried other exhaust shops? See if you can bring in your own brand new cat. Magnaflow (Car-Sound) makes a good one:
http://store.summitracing.com/defaul...8&autoview=sku

You could probably do some digging around the internet and find an even better price. eBay or something...

 

Is the shop quoting you for a brand new y-pipe w/ converter? I can see it costing that much if that is the case, but there are plenty of other options out there. As mentioned above, you can get a Carsound cat. for fifty or sixty bucks and maybe another fifty to have it installed.

 

You can buy a universal 3" in 3" out for $65.00 shipped.
Buy the cat and remove the y-pipe from the car and take it to the shop or a welder. Most will do it for around $20 - $30.

Or throw in a "test pipe".
You can expect louder and smellier exhaust but you will see a very slight HP gain and miliage gain.

I removed my cat and installed a 16" "test glass pack".

If you live anywhere around central KY I have a low mile direct fit catted y-pipe I will sell. Sorry no shipping, too big and awkward.