Ok... I'm not writing this to get rejected by you...but, you have given too little information to address this issue.
Have you monitored your NETWORK TRAFFIC? How many users on the Domain? Are you using SCSI drives on both servers? How much memory do you have vs. how many services on each server? What topography (type network; 100Mb, 10Mb, Tocken..) do you have? And are you using any mix-match topographies where you might use T3, T1, DSL or some other sort? Are you running across routers? How many directories are you replicating and are they REQUIRED? Some replication are NESTED with subdirectories that are not needed.
These questions can help us help you.
Do me a favor and COMMENT here with some of your answers...
Latez-