I have used seafoam on my e36. I would think it would clean the carbon buildup in your 335's (us slow cars don't have that problem
), if you use PCV to pull it into your engine.
I would still do an oil change after using Seafoam. I have no idea how it would affect an e90's sensors though.
My e36 is like a ti85 compared to all the gizmos in my e90.
EDIT: This thread has some seafoam info- looks like you need to be careful how you get the seafoam in your car...
http://www.e90post.com/forums/showth...=280712&page=2
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06 330i 6mt Spt- Eibach Springs, BMW Perf Susp, Supersprint Exhaust, BSW Audio
RIP-94 325i 5mt 4d- M3 springs/susp, Z3 wheels, Chipped, Intake, Exhaust= FUN!