Which FP are you using? The powers for various 550 motors are as follows
FP-0673 291.6W
FP-9012 172.8W
FP-9013 209.3W
FP-9015 185.0W
AM-0912 180.8W
BB-RS550 253.5W
Switching to the FP-0673 (if you can find some) or the BaneBots RS550 might be all you need to do. All of these motors have a free speed of 15k-20k RPM, the free speed of the CIM is 5310RPM.
Source:
http://www.usfirst.org/sites/default...torInfo4.1.pdf