I have not tested this theory, so this could be off-base, but:
Agent Lead Search - Setting this option to ENABLED will allow agents to search for leads and view lead information while paused in the agent interface. Also, if the Agent User Group is allowed to view Call Logs then the agent will be able to view past call notes for any lead that they are viewing information on. Default is DISABLED.
Agent Lead Search Method - If Agent Lead Search is enabled, this setting defines where the agent will be allowed to search for leads. SYSTEM will search the entire system, CAMPAIGNLISTS will search inside all of the active lists within the campaign, CAMPLISTS_ALL will search inside all of the active and inactive lists within the campaign, LIST will search only within the Manual Dial List ID as defined in the campaign. Default is CAMPLISTS_ALL. One of these options with USER_ in front will only search within leads that have the owner field matching the user ID of the agent, the options with GROUP_ in front will only search within leads that have the owner field matching the user group that the user is a member of, the options with TERRITORY_ in front will only search within leads that have the owner field matching the territories that the agent has selected.
I believe that these settings may also affect the manual dial call lead lookup. You should test this before believing it, though.