Well the FDR on your Cyclone is 7.128 (3.3 gear ratio * 2.16 internal ratio).
The FDR on your Tamiya buggy is 9.28 (I believe) which would mean (3.2 gear ratio * 2.9 internal ratio).
I got the 9.28 for the buggy off the Tamiya webiste.
Buggy linky
It says gear ratio so I could be wrong. I don't know if a higher or lower FDR makes the ESC work harder but that could be your problem. What motor and batteries are you using with the buggy? What types of connectors also?