Merge replication downloads process quickly but upload has terrible throughput

I am running merge replication over a WAN. I am using SQL 2008 R2 SP2. The snapshot applies without issues and small amounts of updates process with no problems. When I try to run larger batches (500 inserts/updates), the latency becomes terrible.

When I run the inserts on the publisher, they sync within 20-30 seconds. When I run them on the subscriber, the sync takes close to 10 minutes.

I have tried the slow link agent profile but don't see any differences in the time it takes. Is there somewhere else I can look to see what is causing this issue?

Any advice is appreciated,

Kim