I found some more info here...
http://forums.nasioc.com/forums/show....php?t=1461156
More specifically, post 13
"The "cheap" blue washer fluids being referred to by the OP are methanol, water and some blue dye. Nothing else - no detergents, no glycol. It's washer fluids such as Prestone Bug Wash that contain other undesireable ingredients and -50 degree fluids that contain glycol that must be avoided. If in doubt, refer the the product's MSDS.
The small amount of dye used "being bad" to burn in an engine is a myth. Of course we all know that dye is used in many common motor fuels, as well as aviation fuel and most race fuels.
In a Subaru engine, the water/meth is typically injected downstream of the MAF sensor, so sensor fouling/damage is not an issue either.
I think the largest concern in using washer fluid is the potential for inconsistent methanol content, especially if you are tuned to the edge. Simple solution - get tuned for an appropriate washer fluid and then spike each gallon with a 12 ounce bottle of Heet to ensure minimum methanol content required for the tune.
And yes, you'll still get a very nice gain using cheap, easily available windshield washer fluid. Below is a composite graph of three tunes, the last one using an Aquamist HSF3 system spraying Autozone Valucraft -20 degree blue washer fluid (32% methanol);"