Ironically, the octane rating advertised on the pumps (R+M/2) is somewhat meaningless when considering which gas to use for performance. There are 3 octane ratings and for performance, the one that means the most (MON) is the one you never see expect when looking at the specs for race gas. I would highly recommend a good alky inj system to rid you of the concern about detonation from pump gas especially if your turbo engine is sensitive to pump gas. While there is added expense, what is the cost of having to redo your engine? Another way to look at the added cost is that will allow you ro run more boost safely on pump gas and therefore make more HP. With alky you go from worrying about too much boost causing detonation to actually running more boost.
See below and I highlighted some points.
Research Octane (RON)
CFR tested @ 600 RPM's, fixed timing at 13 degrees BTDC, fuel temp is not controlled and intake air is varied with the barometric pressure. ( This is basically a No-Load test and this number should NEVER be used to determine which fuel to use in your race engine.
Motor Octane (MON)
CFR Tested @ 900 rpms, timing is varied with compression ratio, fuel is preheated to 300 degrees Farenheit, intake air is preheated to 100 degrees Farenheit. Motor Octane, measured under varying load, is definitely the most representative octane measurement for actual engine octane requirements. The closer the Motor Octane number to the Research Octane number the more stable the fuel is throughout the RPM range . This is very critical when running higher that 7500+ RPM's engine speed.
R+M/2
This method of measurement consists of adding together both the MOTOR and RESEARCH Octane numbers and then dividing by two. This is the number in that yellow box that you see on the gas pumps. This number should only be used when determining which fuel to use in your street car or tow vehicle. This method is NOT intended for correct use in your racing engine.