came accross this lil equation/xls doc online that gives you answers on how much additives (toulene,xylene) to add to pump gas to get a higher octane fuel. i found this usefull and beneficial to us since alot are always asking, how much do i have to add to get xx octane. it would be a nice addition to the stickies on home made race fuel in the FI section. im suprised it wasnt in there already.

http://www.gnttype.org/techarea/misc/octaneblend.xls