Hi we need to upload list of lead in Marketo.
Only Sync when they do any activity or reach score to 100.
Is it true because my salesforce and marketo sync is bidirectional
it will always sync all leads in Marketo even I don't run through the Sync to salesforce or add to salesforce campaign.
The lead sync from Marketo end cannot be automatic. There might be one life-cycle campaign running to sync lead to SFDC that you might not aware of.
Where as it will be done automatically from Salesforce.
I would suggest you to deactivate that campaign and create a new smart campaign which will trigger when any lead crosses 100 scores.
Try searching that campaign in campaign inspector.
Hope this helps.