I get these codes on my e89 N54 Z4 35i. Codes 29F4 29F5.
I have not seen a warning light on the dash/idrive and when I check the idrive it says no faults. Car drives fantastic.
I believe it could be caused by BAD FUEL since both cats give the fault code.
BTW my car is brand new - only 3500km done - so chance for BOTH cats to have gone bad at the exact same time is very slim.