The Manage KPI Targets role enables the Dealership KPI Targets, Yard KPI Targets, Salesperson KPI Targets, Lead Sources and screens under Settings>Sales Pipeline Settings.  (Note Campaign visibility is controlled by the Lead Manager Role)

If the User is not ticked they cannot set their KPI's.  If the User is ticked they will have control to set KPI's for all the users who share the role with them.  

Please Note that the role also control access to the Lead Source screen.  If you can view the Lead Source screen you are able to add/edit the Lead Source list and deactivate sources.

If you do not want the User to be able to edit Lead Sources then the User should be REMOVED from the role entirely.  This will only have the effect of removing their access from the KPI and Lead Source screens.  Their managers will still be able to add targets for these users and this does not affect the display or count of targets in reporting.