[infinitenexus]

I'll be moving to New York State (Rochester) in about a year so I do have to pay attention to emissions tests. Also, I don't want to wreck the environment for a few extra horsepower, but with 4 cats on this thing I figured I can remove 2 and find a happy medium. So, which option is better, from a performance perspective while passing emissions tests?

1. Catless headers while retaining stock catted midpipe. I have a 328xi and from what I understand the rear bolts of the exhaust manifold are a bear to get to with the subframe there, so that's something to consider. Otherwise, I feel this is the option to go with for performance (and probably sound).

2. Keep stock exhaust manifolds and remove secondary cats. This would be much, much easier and if I had access to a welder I could simply cut out the cats and weld in pipes. From what I've read, most/all catless midpipes don't fit the awd models as the differential is in the way. This option would be easier and cheaper, assuming I have access to a welder, but would offer less power.

Can I get y'all's thoughts on this one please?

[aphael]

Catless headers sound like the way to go since you want performance. That is the setup I have with stock midpipe. Once hot, doesn't really smell much at all. You would be cutting it close on a sniffer test though.

[Mavus]

headers … 2nd cats a waste of $$$

consider ceramic coating to keep temps lower like Swain tech

[desertman123]

+1 for catless headers + the original secondaries

[infinitenexus]

Ceramic coating is a great idea. I'm saving my pennies right now to pick up a pair, and once the weather turns warmer hopefully I can install them.

I have an xi so fitment can be a bit different with some things, like the midpipes. If I can find another 328xi in a local junkyard I'll grab those midpipes and delete the cats, that way I can run catless and then swap some cats on when it's time for inspections. At least, that's the plan, we'll see if I actually find any in junkyards haha.

[Mavus]

Originally Posted by infinitenexus

Ceramic coating is a great idea. I'm saving my pennies right now to pick up a pair, and once the weather turns warmer hopefully I can install them.

I have an xi so fitment can be a bit different with some things, like the midpipes. If I can find another 328xi in a local junkyard I'll grab those midpipes and delete the cats, that way I can run catless and then swap some cats on when it's time for inspections. At least, that's the plan, we'll see if I actually find any in junkyards haha.

you will also need new bolts for headers … they are one time use

get the best headers you can afford because it will make installation easier and have better flow. As an example Supersprint have perfect fitment.

[infinitenexus]

I actually just picked up a set of Roundelworks headers, as I've read good things about them on here. Now, I just need to wait for spring!