I'm surprised that nobody has mentioned that a catless DP will cause a CEL. Only certain catted DP's won't cause a CEL, Fabspeed being one of them.
Any flash tune can remove the CEL, but since you mentioned being stock, you need to consider this.
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2014 335xi M-Sport 6MT: Estoril Blue II, MHD Stage 2+ , Dinan Exhaust, Dinan CAI, ER Catted DP, ER Chargepipe, AA FMIC.
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