axa,
I did find this in the Heist thread but do not know if the information is accurate.
By SSR22925

"The compression ratio on the 167FMM-M is 9-2.1 and will run fine with 87 grade Petrol. If the head is milled .025" it will raise it to 10.5, if there is enough clearance and it is milled .050" it will bump it up 2 full points. Anything above 10.5 and you should run 93 Octane Petrol. At that point you may also want to invest in a variable CDI one with a potentiometer so you can adjust the spark curve if need be to prevent the dreaded sound of engine knock"