Originally Posted by docpowell

No..no..Ard. I know that you believe that you are the supreme knowledge on all things auto, you are not.
Having owned a few diesel trucks with modified exhausts, I can speak to this. While most aftermarket exhaust are cat back, not all of them are. There are several that are true complete exhausts. Look it up.
Two, I never said that the exhaust systems are not legal to sell, but bypassing the Diesel Exhaust Filtration (DEF) is not street legal due to the emissions requirements, thus these aftermarket parts are sold as "off road use only."
The entire exhaust system is restrictive, the cats, muffler, headers, and pipes, etc.
In the BMW with the UREA system in place, (it can by bypassed.) no one is going to mass produce an aftermarket system for this vehicle because the market isn't there. It is there for the Fords, Chevy's, etc.
And when you bypass the DEF, emissions are changed. So before correcting everyone on these blogs, check yourself. Thanks.