I have a 99 A4 Quattro I was wondering if it's possible to make it dual exhaust... buy 2 cats or something... but I know that catalytic converters have the O2 sensors on them so where would I connect the other sensors to? Anyreplies would be good. thanks

 

just get a high flow cat. and split the flow after the cat. That be easier.

 

Im assuming you have a single pipe 1.8t, well you could splice the O2 sensors or just have a single pipe and then get a y-pipe from the catback.

 

Where do you want the dual exhaust to start? Do you want the dual mufflers like the B6?
Or do you want a full dual exhaust like the S4?

On the 1.8, it doesn't make sense to have a full dual exhaust sense there is only 1 outlet off the turbo.

If you want 2 mufflers, that's not that hard. Just cut the exhaust pipe AFTER the cat, weld in a Y pipe & route the other muffler.

There is no need on a 1.8t to have 2 cats. If you did, you would NOT need to put in another O2, since the car is not set up for it.
You can put a WBO2 in there for YOUR tuning use.

 

I have a 02 a4, and am having an rattle from my exhaust at high rpm's, and when idleing after I have been driving for a bit. I was told by an exhaust guy that the batts in the cats are breaking up, and should be replaced by the dealer. Does anyone know more about this? Or is there a simpler solution or upgrade I should do instead?