The issue will not be the firmware but you can get newer versons from the support download area once you get your account setup and support contract linked.
To troubleshoot bandwidth issues I would start at the interface. Make sure both sides are coming up full duplex and not a half duplex auto-neg somewhere. The interfaces here are FE and equipment for different manufacturers frequently come up half duplex on FE ports between each other. You may have to set explicit settings on one side or the other or both to get a good link.
You already checked that your policies did not have a policer set, also check the physical and bgroup interfaces do not have a bandwidth limit set on them.