50/50 to 75/25 mix...
 

Im running the boost juice mix right now (49 meth/51 water) and i want see how my car does with a 75/25 mix, or close to it.

How much meth should i add to my 50/50 mix to make it a as close as possible to 75/25?

To get to 75/25 you need to add an equal amount of meth to whatever volume of 50/50 you are using, eg. if you have 1 liter of 50/50 adding 1 liter of meth gets you to 75/25. Same goes if you have a gallon of 50/50 you add a gallon of meth.

do it by weight, it is more accurate than volume (as Air- Fuel Ratios are by weight)
I hope you are going to get it retuned when you change the mix ratio