[stilov]

I have an 07 e90. I've catless dps on the way. What are the most restrictive areas on the stock exhaust?
I'd like full exhaust for the weight, but don't want all the noise
I'm thinking the stock mufflers flow pretty well so I might keep those and just go catless.
It seems the consensus is the 2ndary cats are restrictive as well, correct?

[scottp999]

Yes, all the cats are restrictive. I have not looked at an e90 exhaust recently but the e92 has some crushed piping in the design that can't be good.

There is an old thread around where someone discected the stock muffler and showed pictures. You might want look for it.

[stilov]

On my e39 M5 I pulled the cats and put maganflows on it and left the resonator. I liked the sound, not raspy or overbearing. I will pull the cats, but I like the muffler flap. I guess what I am not sure of is should I pull the resonators too? On the M5 it seemed the resonators muffled more than the mufflers.

[Mike@N54Tuning.com]

The stock downpipes are the most restrictive.

Mike