What are you planning for the cats or CEL in the case you opt to not run any?

CEL will pop up on you ... You need to send the ECU to active Autowerk to get it flash.

For the time being I'm gonna run catless and the spark defouler on the post cat O2's. A custom mid-section is cooking on the back burner. Looking at twin 200 cell cats and then merging into a magnaflow tru-x muffler #11385. I may go with mrbmwx5's wisdom and do an AA tune. There is also the option of going with a euro tune, and that would be free. I've got some research to do.

From what I've read, the placement of the cat cannot be too far downstream as the exhaust gasses become too cool. It was mentioned (bimmerforums, iirc) that having a cat after the header is reliable for the most part, but can occasionally throw a CEL. Cutting up those beautiful headers seems taboo to me...

One of my cat cores is rattling around, so ill heading down a similar route (I'm waiting to see your reviews on these)....but in my case ill definitely be tossing in cats somewhere to rid that 50's Buick smell from the exhaust! Lol

With the proper o2 spacer on the post cat o2's you may not even need a custom tune, VW guys run catless all day and as long as you space the rear sensor properly it should not come up on you.

check out a sensor from here www.42draftdesigns.com, its a 90 degree spacer which should work better than just drilling out the spark plug nonfoulers (way to bring back the old trick from 10 years ago!)

MMM.. eye candy can be fun!

These are on my E39..

http://www.my02.com/images/tech/downpipes.jpg

Holy Hell! I'm pretty sure that's not just eye candy, that's pure car porn. Very nice e39!

IIRC, WallyX5 had a set of 3-series headers on his 300k+ miles 3.0i awhile back.

Show off :D :thumbup:

Did you get a V6...?

This is relevant to my interests...in to see how it turns out :thumbup: