If you're 951 has serious mods 110 will make a BIG difference because it resists knock much more than 91 or 92 octane. From first hand experience i can tell you that if you can run one of these cars over 20 psi with no knock you will be FLYIN - I will guarntee you that. Its really a simple issue and this is why racers use high-ocatane fuel - to prevent knock. The real challenge, at least out here in So Cal, is getting a 951 to run right on the 91 octane squirrel pee. Most will tell you no more than 15 psi on this stuff.
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Erick
86 951
http://www.pelicanparts.com/cgi-bin/pmpre/pm.cgi?action=display&login=aka_951