Cracked valve cover be a cause of smoke?

[Ultimateone]

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[Solo_M_Tech]

getting rid of the secondary cats has been known to cause an increase in smoke in the exhaust, the exact cause is debateable, but most likely the turbo seals. However, if the valve cover was leaking, cuasing smoke, it would be under the hood most likely, and you'd see oil residue on the passenger side of the engine, and exhaust/turbo.

[Ultimateone]

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[Solo_M_Tech]

Originally Posted by Ultimateone

Yeah I'm betting its the turbos, maybe BMW will replace mine but I'm doubting it even with the warranty on them. Yes, no smoke from under the hood so thats a good sign. I'm putting cats back in the mids this weekend too, gonna miss the burbles and pops

It's not just the secondary cats. The primary kitties apply alittle back pressure to the turbo to help the seals do their job. Without that back pressure you'll get alittle smoke. Especially with a tune and or old turbos. Good luck!