The MDS engines are high compression and designed for zero nitro, FAI fuel, alcohol and oil only fuel. The OS #8 is/was the plug of choice but they ran better with very low nitro, 5% worked pretty well. Some of the other guys started mixing there own FAI fuel when we were trying to figure these engines out. Me being a lazy ass just bought some Power Master 5% and got them running OK. People that want to bother can do a search here on RCU and read up on what others did to try to get them running. The engines were here in about the mid 90s? You can get the exact dates from Horizon just by phoning them. Russia's pay back for the Wall!!!