Gotfour

Is this a difficult task for the home mechanic? ..........Rattling sound like
b-b's in a trash can, I think its the cat coming apart. Is the Flowmaster unit a good option for replacement?

Injuneer

If you have the stock Y-pipe, the cat is welded to the pipe, and has to be cut off. The new one will probably require that it be welded in. The stock intermediate pipe has a flange that will need a matching flange on the cat.

Is this a 49-state car (single cat) or an A4 with CA-emissions (dual cat)?

I have not seen anyone here indicate they have used the Flowmaster cat. Is it a direct replacement?

Gotfour

This looks like a total replacement for the "Y" and cat.......
http://www.summitracing.com/parts/fl...FSdk7AodHC8Adg

Chet1185

That looks good, and cheaper than stock replacement. Just use pb blaster and heat, should be fairly easy.

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AdsoYo

I've been using Magnaflow's cat since 2007 and it's been working fine for me. I bought the universal cat, part number 94009 because it was cheaper and I was using Mac headers and Y pipe. The cat had to be welded onto my cat-back and it mates to the Y pipe with a ball flange. I think this cat flows something like 450 cfm which isn't that far behind the high-flow Random tech cat which flows something like 550 cfm.