lmp to engine size

can any one tell me that the recomended lpm of hho i should have for a 5.7L TBI engine. i am thinking i want 4-5 Lpm i am wanting to get about 5 miles per gallon more then what i get now.
i am also interested in knowing if anyone has piped this in off of the EGR vaccume line instead of into the intake.
i was also thinking that because i have the mass flow air cleaner and intake on my engine that i will be able to pump hho into the system get a increase in gas milage and not have to screw with my o2 sensor. but if i do pipe this into my intake i think i should have a better and more even mix of the hho, air, and atomized gas because of the extra flow from the after market intake as well as the vortex the tube is suposed to make just obove the tbi. what do you guys think?