Customers often ask me for tips for improving the integration, specifically the sync speed, between Marketo and SFDC. The syncing of a lot of fields can impact performance. Here is a list of things you can do to optimize the field sync between the two systems.
Bonus tip: Remember to evaluate all the fields syncing between the two systems for all SFDC objects. Start with the Opportunity and Account objects but don’t neglect looking at any custom objects that are syncing.
Here are some additional resources for learning about the Marketo integration with SFDC.