pulleys can shred the belt or push the psi to high for the engine components to handle thus causing severe problems to many different components... none of the typical pulleys sold by evosport renntech kleemann will likely do this but it is possible, also be aware that custom pulleys and hennesey pulleys can potential cause these problems if not built correctly.

as for the ecu... i know too little about it to really say much, but if the ecu is programmed to handle fuels of 93 octane and you fill it up with the 91 premium that can potentially cause a problem... other than that others will better be able to answer your question.