lsufan

No one that I know of w/o ECU programming. I was tempted to do the same, but after speaking the RennTech, Brabus and Kleeman, I decided against it while under warranty. I would imagine a 300 metallic substrate of good quality would be more efficient in burning carbon the stock primaries. That being said, as post 02 sensors do play a role in fuel adaptation, I didn't want to risk it w/o a full dyno run to be sure A/F are all ok.

AMS Performance

You can easily get away with it on 300 cell high flow metal core cats. On some cars you can easily get away with even 200-cell primaries and no CEL light. The primary O2s are the ones that do most of the work, the secondaries are just there to check to see if the cats are actually doing anything (of if they even exist). Start of by installing high flow 2nd cats and then later on if you want to do primaries. However keep in mind, the stock primary cats are metal core, the secondary cats are ceramic (and these fail frequently and are much larger and more restrictive overall), so replace the secondaries for more power & better sound and you should be happy.

imducati

thanks for the great responses, I'll let you know how it goes.

A' La F1

Folks have been wondering where I got the cats on ebay. I bought them from this company, but I cannot find them on ebay for some reason. Do a search for ebay seller "ppe" - it may work. I paid $200 plus shipping - they will give you a discount for buying two.

http://www.ppeengineering.com/fabparts.htm

JRHolt

I think that this is the eBay link: Peren Performance Exhaust Supply

linh811

wow you went through a lot of work. I just went the cheap route: 2nd cat delete, xpipe, muffler delete. I had them cut the pipes immediately after the 02 sensors to get ride of that squished, crimped, 90 bend right before the stock 2nd cats. Love the sound of my car.

took delivery of my car just 3 days ago (83 miles on the odo), probably wait a few months before i try replacing the primary cats with 300cell racing cats.