I assume this means moving from NFS v3 to NFS v4. In that case you might use the opportunity to check if you are using the optimum block size in the mount parameters. In my case I found considerable increase in throughput by first finding the optimum block size and then setting it in the mount options. I used IOZone to test this:
./iozone -Racb moodlecl22nfsmoodle.wks -g 1G -y 1 -q 128k -i0 -i1 -U /mnt/lms/moodle -f /mnt/lms/moodle/iozone/prufuskra.bin
Found that the optimum block size was 16 KB and set the mount parameters accordingly:
mount -o rw,vers=4,addr=22.214.171.124,clientaddr=126.96.36.199,nodiratime,noatime,rsize=16384,wsize=16384 /mnt/lms/moodle
You also might want to check that the TCP and UDP packets from the NFS connection, are not obstructed by firewalls. That kills performance.